The DRBD driver

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

19 files changed, 20366 insertions, 0 deletions

diff --git a/drivers/block/Kconfig b/drivers/block/Kconfig
index 1d886e079c58..77bfce52e9ca 100644
--- a/drivers/block/Kconfig
+++ b/drivers/block/Kconfig
@@ -271,6 +271,8 @@ config BLK_DEV_CRYPTOLOOP
           instead, which can be configured to be on-disk compatible with the
           cryptoloop device.
 
+source "drivers/block/drbd/Kconfig"
+
 config BLK_DEV_NBD
         tristate "Network block device support"
         depends on NET
diff --git a/drivers/block/Makefile b/drivers/block/Makefile
index cdaa3f8fddf0..aff5ac925c34 100644
--- a/drivers/block/Makefile
+++ b/drivers/block/Makefile
@@ -36,5 +36,6 @@ obj-$(CONFIG_BLK_DEV_UB)	+= ub.o
 obj-$(CONFIG_BLK_DEV_HD)        += hd.o
 
 obj-$(CONFIG_XEN_BLKDEV_FRONTEND)       += xen-blkfront.o
+obj-$(CONFIG_BLK_DEV_DRBD)     += drbd/
 
 swim_mod-objs   := swim.o swim_asm.o
diff --git a/drivers/block/drbd/Kconfig b/drivers/block/drbd/Kconfig
new file mode 100644
index 000000000000..4e6f90f487c2
--- /dev/null
+++ b/drivers/block/drbd/Kconfig
@@ -0,0 +1,82 @@
+#
+# DRBD device driver configuration
+#
+
+comment "DRBD disabled because PROC_FS, INET or CONNECTOR not selected"
+        depends on !PROC_FS || !INET || !CONNECTOR
+
+config BLK_DEV_DRBD
+        tristate "DRBD Distributed Replicated Block Device support"
+        depends on PROC_FS && INET && CONNECTOR
+        select LRU_CACHE
+        default n
+        help
+
+          NOTE: In order to authenticate connections you have to select
+          CRYPTO_HMAC and a hash function as well.
+
+          DRBD is a shared-nothing, synchronously replicated block device. It
+          is designed to serve as a building block for high availability
+          clusters and in this context, is a "drop-in" replacement for shared
+          storage. Simplistically, you could see it as a network RAID 1.
+
+          Each minor device has a role, which can be 'primary' or 'secondary'.
+          On the node with the primary device the application is supposed to
+          run and to access the device (/dev/drbdX). Every write is sent to
+          the local 'lower level block device' and, across the network, to the
+          node with the device in 'secondary' state.  The secondary device
+          simply writes the data to its lower level block device.
+
+          DRBD can also be used in dual-Primary mode (device writable on both
+          nodes), which means it can exhibit shared disk semantics in a
+          shared-nothing cluster.  Needless to say, on top of dual-Primary
+          DRBD utilizing a cluster file system is necessary to maintain for
+          cache coherency.
+
+          For automatic failover you need a cluster manager (e.g. heartbeat).
+          See also: http://www.drbd.org/, http://www.linux-ha.org
+
+          If unsure, say N.
+
+config DRBD_TRACE
+        tristate "DRBD tracing"
+        depends on BLK_DEV_DRBD
+        select TRACEPOINTS
+        default n
+        help
+
+          Say Y here if you want to be able to trace various events in DRBD.
+
+          If unsure, say N.
+
+config DRBD_FAULT_INJECTION
+        bool "DRBD fault injection"
+        depends on BLK_DEV_DRBD
+        help
+
+          Say Y here if you want to simulate IO errors, in order to test DRBD's
+          behavior.
+
+          The actual simulation of IO errors is done by writing 3 values to
+          /sys/module/drbd/parameters/
+
+          enable_faults: bitmask of...
+          1     meta data write
+          2               read
+          4     resync data write
+          8                 read
+          16    data write
+          32    data read
+          64    read ahead
+          128   kmalloc of bitmap
+          256   allocation of EE (epoch_entries)
+
+          fault_devs: bitmask of minor numbers
+          fault_rate: frequency in percent
+
+          Example: Simulate data write errors on /dev/drbd0 with a probability of 5%.
+                echo 16 > /sys/module/drbd/parameters/enable_faults
+                echo 1 > /sys/module/drbd/parameters/fault_devs
+                echo 5 > /sys/module/drbd/parameters/fault_rate
+
+          If unsure, say N.
diff --git a/drivers/block/drbd/Makefile b/drivers/block/drbd/Makefile
new file mode 100644
index 000000000000..7d86ef8a8b40
--- /dev/null
+++ b/drivers/block/drbd/Makefile
@@ -0,0 +1,8 @@
+drbd-y := drbd_bitmap.o drbd_proc.o
+drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
+drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
+
+drbd_trace-y := drbd_tracing.o
+
+obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o
+obj-$(CONFIG_DRBD_TRACE)       += drbd_trace.o
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
new file mode 100644
index 000000000000..74b4835d3107
--- /dev/null
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -0,0 +1,1484 @@
+/*
+   drbd_actlog.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_wrappers.h"
+
+/* We maintain a trivial check sum in our on disk activity log.
+ * With that we can ensure correct operation even when the storage
+ * device might do a partial (last) sector write while loosing power.
+ */
+struct __packed al_transaction {
+        u32       magic;
+        u32       tr_number;
+        struct __packed {
+                u32 pos;
+                u32 extent; } updates[1 + AL_EXTENTS_PT];
+        u32       xor_sum;
+};
+
+struct update_odbm_work {
+        struct drbd_work w;
+        unsigned int enr;
+};
+
+struct update_al_work {
+        struct drbd_work w;
+        struct lc_element *al_ext;
+        struct completion event;
+        unsigned int enr;
+        /* if old_enr != LC_FREE, write corresponding bitmap sector, too */
+        unsigned int old_enr;
+};
+
+struct drbd_atodb_wait {
+        atomic_t           count;
+        struct completion  io_done;
+        struct drbd_conf   *mdev;
+        int                error;
+};
+
+
+int w_al_write_transaction(struct drbd_conf *, struct drbd_work *, int);
+
+/* The actual tracepoint needs to have constant number of known arguments...
+ */
+void trace_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, ...)
+{
+        va_list ap;
+
+        va_start(ap, fmt);
+        trace__drbd_resync(mdev, level, fmt, ap);
+        va_end(ap);
+}
+
+static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
+                                 struct drbd_backing_dev *bdev,
+                                 struct page *page, sector_t sector,
+                                 int rw, int size)
+{
+        struct bio *bio;
+        struct drbd_md_io md_io;
+        int ok;
+
+        md_io.mdev = mdev;
+        init_completion(&md_io.event);
+        md_io.error = 0;
+
+        if ((rw & WRITE) && !test_bit(MD_NO_BARRIER, &mdev->flags))
+                rw |= (1 << BIO_RW_BARRIER);
+        rw |= ((1<<BIO_RW_UNPLUG) | (1<<BIO_RW_SYNCIO));
+
+ retry:
+        bio = bio_alloc(GFP_NOIO, 1);
+        bio->bi_bdev = bdev->md_bdev;
+        bio->bi_sector = sector;
+        ok = (bio_add_page(bio, page, size, 0) == size);
+        if (!ok)
+                goto out;
+        bio->bi_private = &md_io;
+        bio->bi_end_io = drbd_md_io_complete;
+        bio->bi_rw = rw;
+
+        trace_drbd_bio(mdev, "Md", bio, 0, NULL);
+
+        if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD))
+                bio_endio(bio, -EIO);
+        else
+                submit_bio(rw, bio);
+        wait_for_completion(&md_io.event);
+        ok = bio_flagged(bio, BIO_UPTODATE) && md_io.error == 0;
+
+        /* check for unsupported barrier op.
+         * would rather check on EOPNOTSUPP, but that is not reliable.
+         * don't try again for ANY return value != 0 */
+        if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER) && !ok)) {
+                /* Try again with no barrier */
+                dev_warn(DEV, "Barriers not supported on meta data device - disabling\n");
+                set_bit(MD_NO_BARRIER, &mdev->flags);
+                rw &= ~(1 << BIO_RW_BARRIER);
+                bio_put(bio);
+                goto retry;
+        }
+ out:
+        bio_put(bio);
+        return ok;
+}
+
+int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
+                         sector_t sector, int rw)
+{
+        int logical_block_size, mask, ok;
+        int offset = 0;
+        struct page *iop = mdev->md_io_page;
+
+        D_ASSERT(mutex_is_locked(&mdev->md_io_mutex));
+
+        BUG_ON(!bdev->md_bdev);
+
+        logical_block_size = bdev_logical_block_size(bdev->md_bdev);
+        if (logical_block_size == 0)
+                logical_block_size = MD_SECTOR_SIZE;
+
+        /* in case logical_block_size != 512 [ s390 only? ] */
+        if (logical_block_size != MD_SECTOR_SIZE) {
+                mask = (logical_block_size / MD_SECTOR_SIZE) - 1;
+                D_ASSERT(mask == 1 || mask == 3 || mask == 7);
+                D_ASSERT(logical_block_size == (mask+1) * MD_SECTOR_SIZE);
+                offset = sector & mask;
+                sector = sector & ~mask;
+                iop = mdev->md_io_tmpp;
+
+                if (rw & WRITE) {
+                        /* these are GFP_KERNEL pages, pre-allocated
+                         * on device initialization */
+                        void *p = page_address(mdev->md_io_page);
+                        void *hp = page_address(mdev->md_io_tmpp);
+
+                        ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector,
+                                        READ, logical_block_size);
+
+                        if (unlikely(!ok)) {
+                                dev_err(DEV, "drbd_md_sync_page_io(,%llus,"
+                                    "READ [logical_block_size!=512]) failed!\n",
+                                    (unsigned long long)sector);
+                                return 0;
+                        }
+
+                        memcpy(hp + offset*MD_SECTOR_SIZE, p, MD_SECTOR_SIZE);
+                }
+        }
+
+        if (sector < drbd_md_first_sector(bdev) ||
+            sector > drbd_md_last_sector(bdev))
+                dev_alert(DEV, "%s [%d]:%s(,%llus,%s) out of range md access!\n",
+                     current->comm, current->pid, __func__,
+                     (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+
+        ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, logical_block_size);
+        if (unlikely(!ok)) {
+                dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed!\n",
+                    (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
+                return 0;
+        }
+
+        if (logical_block_size != MD_SECTOR_SIZE && !(rw & WRITE)) {
+                void *p = page_address(mdev->md_io_page);
+                void *hp = page_address(mdev->md_io_tmpp);
+
+                memcpy(p, hp + offset*MD_SECTOR_SIZE, MD_SECTOR_SIZE);
+        }
+
+        return ok;
+}
+
+static struct lc_element *_al_get(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *al_ext;
+        struct lc_element *tmp;
+        unsigned long     al_flags = 0;
+
+        spin_lock_irq(&mdev->al_lock);
+        tmp = lc_find(mdev->resync, enr/AL_EXT_PER_BM_SECT);
+        if (unlikely(tmp != NULL)) {
+                struct bm_extent  *bm_ext = lc_entry(tmp, struct bm_extent, lce);
+                if (test_bit(BME_NO_WRITES, &bm_ext->flags)) {
+                        spin_unlock_irq(&mdev->al_lock);
+                        return NULL;
+                }
+        }
+        al_ext   = lc_get(mdev->act_log, enr);
+        al_flags = mdev->act_log->flags;
+        spin_unlock_irq(&mdev->al_lock);
+
+        /*
+        if (!al_ext) {
+                if (al_flags & LC_STARVING)
+                        dev_warn(DEV, "Have to wait for LRU element (AL too small?)\n");
+                if (al_flags & LC_DIRTY)
+                        dev_warn(DEV, "Ongoing AL update (AL device too slow?)\n");
+        }
+        */
+
+        return al_ext;
+}
+
+void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+        struct lc_element *al_ext;
+        struct update_al_work al_work;
+
+        D_ASSERT(atomic_read(&mdev->local_cnt) > 0);
+
+        trace_drbd_actlog(mdev, sector, "al_begin_io");
+
+        wait_event(mdev->al_wait, (al_ext = _al_get(mdev, enr)));
+
+        if (al_ext->lc_number != enr) {
+                /* drbd_al_write_transaction(mdev,al_ext,enr);
+                 * recurses into generic_make_request(), which
+                 * disallows recursion, bios being serialized on the
+                 * current->bio_tail list now.
+                 * we have to delegate updates to the activity log
+                 * to the worker thread. */
+                init_completion(&al_work.event);
+                al_work.al_ext = al_ext;
+                al_work.enr = enr;
+                al_work.old_enr = al_ext->lc_number;
+                al_work.w.cb = w_al_write_transaction;
+                drbd_queue_work_front(&mdev->data.work, &al_work.w);
+                wait_for_completion(&al_work.event);
+
+                mdev->al_writ_cnt++;
+
+                spin_lock_irq(&mdev->al_lock);
+                lc_changed(mdev->act_log, al_ext);
+                spin_unlock_irq(&mdev->al_lock);
+                wake_up(&mdev->al_wait);
+        }
+}
+
+void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+        struct lc_element *extent;
+        unsigned long flags;
+
+        trace_drbd_actlog(mdev, sector, "al_complete_io");
+
+        spin_lock_irqsave(&mdev->al_lock, flags);
+
+        extent = lc_find(mdev->act_log, enr);
+
+        if (!extent) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                dev_err(DEV, "al_complete_io() called on inactive extent %u\n", enr);
+                return;
+        }
+
+        if (lc_put(mdev->act_log, extent) == 0)
+                wake_up(&mdev->al_wait);
+
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+int
+w_al_write_transaction(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct update_al_work *aw = container_of(w, struct update_al_work, w);
+        struct lc_element *updated = aw->al_ext;
+        const unsigned int new_enr = aw->enr;
+        const unsigned int evicted = aw->old_enr;
+        struct al_transaction *buffer;
+        sector_t sector;
+        int i, n, mx;
+        unsigned int extent_nr;
+        u32 xor_sum = 0;
+
+        if (!get_ldev(mdev)) {
+                dev_err(DEV, "get_ldev() failed in w_al_write_transaction\n");
+                complete(&((struct update_al_work *)w)->event);
+                return 1;
+        }
+        /* do we have to do a bitmap write, first?
+         * TODO reduce maximum latency:
+         * submit both bios, then wait for both,
+         * instead of doing two synchronous sector writes. */
+        if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)
+                drbd_bm_write_sect(mdev, evicted/AL_EXT_PER_BM_SECT);
+
+        mutex_lock(&mdev->md_io_mutex); /* protects md_io_page, al_tr_cycle, ... */
+        buffer = (struct al_transaction *)page_address(mdev->md_io_page);
+
+        buffer->magic = __constant_cpu_to_be32(DRBD_MAGIC);
+        buffer->tr_number = cpu_to_be32(mdev->al_tr_number);
+
+        n = lc_index_of(mdev->act_log, updated);
+
+        buffer->updates[0].pos = cpu_to_be32(n);
+        buffer->updates[0].extent = cpu_to_be32(new_enr);
+
+        xor_sum ^= new_enr;
+
+        mx = min_t(int, AL_EXTENTS_PT,
+                   mdev->act_log->nr_elements - mdev->al_tr_cycle);
+        for (i = 0; i < mx; i++) {
+                unsigned idx = mdev->al_tr_cycle + i;
+                extent_nr = lc_element_by_index(mdev->act_log, idx)->lc_number;
+                buffer->updates[i+1].pos = cpu_to_be32(idx);
+                buffer->updates[i+1].extent = cpu_to_be32(extent_nr);
+                xor_sum ^= extent_nr;
+        }
+        for (; i < AL_EXTENTS_PT; i++) {
+                buffer->updates[i+1].pos = __constant_cpu_to_be32(-1);
+                buffer->updates[i+1].extent = __constant_cpu_to_be32(LC_FREE);
+                xor_sum ^= LC_FREE;
+        }
+        mdev->al_tr_cycle += AL_EXTENTS_PT;
+        if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
+                mdev->al_tr_cycle = 0;
+
+        buffer->xor_sum = cpu_to_be32(xor_sum);
+
+        sector =  mdev->ldev->md.md_offset
+                + mdev->ldev->md.al_offset + mdev->al_tr_pos;
+
+        if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE))
+                drbd_chk_io_error(mdev, 1, TRUE);
+
+        if (++mdev->al_tr_pos >
+            div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+                mdev->al_tr_pos = 0;
+
+        D_ASSERT(mdev->al_tr_pos < MD_AL_MAX_SIZE);
+        mdev->al_tr_number++;
+
+        mutex_unlock(&mdev->md_io_mutex);
+
+        complete(&((struct update_al_work *)w)->event);
+        put_ldev(mdev);
+
+        return 1;
+}
+
+/**
+ * drbd_al_read_tr() - Read a single transaction from the on disk activity log
+ * @mdev:       DRBD device.
+ * @bdev:       Block device to read form.
+ * @b:          pointer to an al_transaction.
+ * @index:      On disk slot of the transaction to read.
+ *
+ * Returns -1 on IO error, 0 on checksum error and 1 upon success.
+ */
+static int drbd_al_read_tr(struct drbd_conf *mdev,
+                           struct drbd_backing_dev *bdev,
+                           struct al_transaction *b,
+                           int index)
+{
+        sector_t sector;
+        int rv, i;
+        u32 xor_sum = 0;
+
+        sector = bdev->md.md_offset + bdev->md.al_offset + index;
+
+        /* Dont process error normally,
+         * as this is done before disk is attached! */
+        if (!drbd_md_sync_page_io(mdev, bdev, sector, READ))
+                return -1;
+
+        rv = (be32_to_cpu(b->magic) == DRBD_MAGIC);
+
+        for (i = 0; i < AL_EXTENTS_PT + 1; i++)
+                xor_sum ^= be32_to_cpu(b->updates[i].extent);
+        rv &= (xor_sum == be32_to_cpu(b->xor_sum));
+
+        return rv;
+}
+
+/**
+ * drbd_al_read_log() - Restores the activity log from its on disk representation.
+ * @mdev:       DRBD device.
+ * @bdev:       Block device to read form.
+ *
+ * Returns 1 on success, returns 0 when reading the log failed due to IO errors.
+ */
+int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+        struct al_transaction *buffer;
+        int i;
+        int rv;
+        int mx;
+        int active_extents = 0;
+        int transactions = 0;
+        int found_valid = 0;
+        int from = 0;
+        int to = 0;
+        u32 from_tnr = 0;
+        u32 to_tnr = 0;
+        u32 cnr;
+
+        mx = div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT);
+
+        /* lock out all other meta data io for now,
+         * and make sure the page is mapped.
+         */
+        mutex_lock(&mdev->md_io_mutex);
+        buffer = page_address(mdev->md_io_page);
+
+        /* Find the valid transaction in the log */
+        for (i = 0; i <= mx; i++) {
+                rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+                if (rv == 0)
+                        continue;
+                if (rv == -1) {
+                        mutex_unlock(&mdev->md_io_mutex);
+                        return 0;
+                }
+                cnr = be32_to_cpu(buffer->tr_number);
+
+                if (++found_valid == 1) {
+                        from = i;
+                        to = i;
+                        from_tnr = cnr;
+                        to_tnr = cnr;
+                        continue;
+                }
+                if ((int)cnr - (int)from_tnr < 0) {
+                        D_ASSERT(from_tnr - cnr + i - from == mx+1);
+                        from = i;
+                        from_tnr = cnr;
+                }
+                if ((int)cnr - (int)to_tnr > 0) {
+                        D_ASSERT(cnr - to_tnr == i - to);
+                        to = i;
+                        to_tnr = cnr;
+                }
+        }
+
+        if (!found_valid) {
+                dev_warn(DEV, "No usable activity log found.\n");
+                mutex_unlock(&mdev->md_io_mutex);
+                return 1;
+        }
+
+        /* Read the valid transactions.
+         * dev_info(DEV, "Reading from %d to %d.\n",from,to); */
+        i = from;
+        while (1) {
+                int j, pos;
+                unsigned int extent_nr;
+                unsigned int trn;
+
+                rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+                ERR_IF(rv == 0) goto cancel;
+                if (rv == -1) {
+                        mutex_unlock(&mdev->md_io_mutex);
+                        return 0;
+                }
+
+                trn = be32_to_cpu(buffer->tr_number);
+
+                spin_lock_irq(&mdev->al_lock);
+
+                /* This loop runs backwards because in the cyclic
+                   elements there might be an old version of the
+                   updated element (in slot 0). So the element in slot 0
+                   can overwrite old versions. */
+                for (j = AL_EXTENTS_PT; j >= 0; j--) {
+                        pos = be32_to_cpu(buffer->updates[j].pos);
+                        extent_nr = be32_to_cpu(buffer->updates[j].extent);
+
+                        if (extent_nr == LC_FREE)
+                                continue;
+
+                        lc_set(mdev->act_log, extent_nr, pos);
+                        active_extents++;
+                }
+                spin_unlock_irq(&mdev->al_lock);
+
+                transactions++;
+
+cancel:
+                if (i == to)
+                        break;
+                i++;
+                if (i > mx)
+                        i = 0;
+        }
+
+        mdev->al_tr_number = to_tnr+1;
+        mdev->al_tr_pos = to;
+        if (++mdev->al_tr_pos >
+            div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
+                mdev->al_tr_pos = 0;
+
+        /* ok, we are done with it */
+        mutex_unlock(&mdev->md_io_mutex);
+
+        dev_info(DEV, "Found %d transactions (%d active extents) in activity log.\n",
+             transactions, active_extents);
+
+        return 1;
+}
+
+static void atodb_endio(struct bio *bio, int error)
+{
+        struct drbd_atodb_wait *wc = bio->bi_private;
+        struct drbd_conf *mdev = wc->mdev;
+        struct page *page;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+        /* strange behavior of some lower level drivers...
+         * fail the request by clearing the uptodate flag,
+         * but do not return any error?! */
+        if (!error && !uptodate)
+                error = -EIO;
+
+        drbd_chk_io_error(mdev, error, TRUE);
+        if (error && wc->error == 0)
+                wc->error = error;
+
+        if (atomic_dec_and_test(&wc->count))
+                complete(&wc->io_done);
+
+        page = bio->bi_io_vec[0].bv_page;
+        put_page(page);
+        bio_put(bio);
+        mdev->bm_writ_cnt++;
+        put_ldev(mdev);
+}
+
+#define S2W(s)  ((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* activity log to on disk bitmap -- prepare bio unless that sector
+ * is already covered by previously prepared bios */
+static int atodb_prepare_unless_covered(struct drbd_conf *mdev,
+                                        struct bio **bios,
+                                        unsigned int enr,
+                                        struct drbd_atodb_wait *wc) __must_hold(local)
+{
+        struct bio *bio;
+        struct page *page;
+        sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+                                      + mdev->ldev->md.bm_offset;
+        unsigned int page_offset = PAGE_SIZE;
+        int offset;
+        int i = 0;
+        int err = -ENOMEM;
+
+        /* Check if that enr is already covered by an already created bio.
+         * Caution, bios[] is not NULL terminated,
+         * but only initialized to all NULL.
+         * For completely scattered activity log,
+         * the last invocation iterates over all bios,
+         * and finds the last NULL entry.
+         */
+        while ((bio = bios[i])) {
+                if (bio->bi_sector == on_disk_sector)
+                        return 0;
+                i++;
+        }
+        /* bios[i] == NULL, the next not yet used slot */
+
+        /* GFP_KERNEL, we are not in the write-out path */
+        bio = bio_alloc(GFP_KERNEL, 1);
+        if (bio == NULL)
+                return -ENOMEM;
+
+        if (i > 0) {
+                const struct bio_vec *prev_bv = bios[i-1]->bi_io_vec;
+                page_offset = prev_bv->bv_offset + prev_bv->bv_len;
+                page = prev_bv->bv_page;
+        }
+        if (page_offset == PAGE_SIZE) {
+                page = alloc_page(__GFP_HIGHMEM);
+                if (page == NULL)
+                        goto out_bio_put;
+                page_offset = 0;
+        } else {
+                get_page(page);
+        }
+
+        offset = S2W(enr);
+        drbd_bm_get_lel(mdev, offset,
+                        min_t(size_t, S2W(1), drbd_bm_words(mdev) - offset),
+                        kmap(page) + page_offset);
+        kunmap(page);
+
+        bio->bi_private = wc;
+        bio->bi_end_io = atodb_endio;
+        bio->bi_bdev = mdev->ldev->md_bdev;
+        bio->bi_sector = on_disk_sector;
+
+        if (bio_add_page(bio, page, MD_SECTOR_SIZE, page_offset) != MD_SECTOR_SIZE)
+                goto out_put_page;
+
+        atomic_inc(&wc->count);
+        /* we already know that we may do this...
+         * get_ldev_if_state(mdev,D_ATTACHING);
+         * just get the extra reference, so that the local_cnt reflects
+         * the number of pending IO requests DRBD at its backing device.
+         */
+        atomic_inc(&mdev->local_cnt);
+
+        bios[i] = bio;
+
+        return 0;
+
+out_put_page:
+        err = -EINVAL;
+        put_page(page);
+out_bio_put:
+        bio_put(bio);
+        return err;
+}
+
+/**
+ * drbd_al_to_on_disk_bm() -  * Writes bitmap parts covered by active AL extents
+ * @mdev:       DRBD device.
+ *
+ * Called when we detach (unconfigure) local storage,
+ * or when we go from R_PRIMARY to R_SECONDARY role.
+ */
+void drbd_al_to_on_disk_bm(struct drbd_conf *mdev)
+{
+        int i, nr_elements;
+        unsigned int enr;
+        struct bio **bios;
+        struct drbd_atodb_wait wc;
+
+        ERR_IF (!get_ldev_if_state(mdev, D_ATTACHING))
+                return; /* sorry, I don't have any act_log etc... */
+
+        wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+        nr_elements = mdev->act_log->nr_elements;
+
+        /* GFP_KERNEL, we are not in anyone's write-out path */
+        bios = kzalloc(sizeof(struct bio *) * nr_elements, GFP_KERNEL);
+        if (!bios)
+                goto submit_one_by_one;
+
+        atomic_set(&wc.count, 0);
+        init_completion(&wc.io_done);
+        wc.mdev = mdev;
+        wc.error = 0;
+
+        for (i = 0; i < nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                /* next statement also does atomic_inc wc.count and local_cnt */
+                if (atodb_prepare_unless_covered(mdev, bios,
+                                                enr/AL_EXT_PER_BM_SECT,
+                                                &wc))
+                        goto free_bios_submit_one_by_one;
+        }
+
+        /* unnecessary optimization? */
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+
+        /* all prepared, submit them */
+        for (i = 0; i < nr_elements; i++) {
+                if (bios[i] == NULL)
+                        break;
+                if (FAULT_ACTIVE(mdev, DRBD_FAULT_MD_WR)) {
+                        bios[i]->bi_rw = WRITE;
+                        bio_endio(bios[i], -EIO);
+                } else {
+                        submit_bio(WRITE, bios[i]);
+                }
+        }
+
+        drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+
+        /* always (try to) flush bitmap to stable storage */
+        drbd_md_flush(mdev);
+
+        /* In case we did not submit a single IO do not wait for
+         * them to complete. ( Because we would wait forever here. )
+         *
+         * In case we had IOs and they are already complete, there
+         * is not point in waiting anyways.
+         * Therefore this if () ... */
+        if (atomic_read(&wc.count))
+                wait_for_completion(&wc.io_done);
+
+        put_ldev(mdev);
+
+        kfree(bios);
+        return;
+
+ free_bios_submit_one_by_one:
+        /* free everything by calling the endio callback directly. */
+        for (i = 0; i < nr_elements && bios[i]; i++)
+                bio_endio(bios[i], 0);
+
+        kfree(bios);
+
+ submit_one_by_one:
+        dev_warn(DEV, "Using the slow drbd_al_to_on_disk_bm()\n");
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                /* Really slow: if we have al-extents 16..19 active,
+                 * sector 4 will be written four times! Synchronous! */
+                drbd_bm_write_sect(mdev, enr/AL_EXT_PER_BM_SECT);
+        }
+
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+        put_ldev(mdev);
+}
+
+/**
+ * drbd_al_apply_to_bm() - Sets the bitmap to diry(1) where covered ba active AL extents
+ * @mdev:       DRBD device.
+ */
+void drbd_al_apply_to_bm(struct drbd_conf *mdev)
+{
+        unsigned int enr;
+        unsigned long add = 0;
+        char ppb[10];
+        int i;
+
+        wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                enr = lc_element_by_index(mdev->act_log, i)->lc_number;
+                if (enr == LC_FREE)
+                        continue;
+                add += drbd_bm_ALe_set_all(mdev, enr);
+        }
+
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+
+        dev_info(DEV, "Marked additional %s as out-of-sync based on AL.\n",
+             ppsize(ppb, Bit2KB(add)));
+}
+
+static int _try_lc_del(struct drbd_conf *mdev, struct lc_element *al_ext)
+{
+        int rv;
+
+        spin_lock_irq(&mdev->al_lock);
+        rv = (al_ext->refcnt == 0);
+        if (likely(rv))
+                lc_del(mdev->act_log, al_ext);
+        spin_unlock_irq(&mdev->al_lock);
+
+        return rv;
+}
+
+/**
+ * drbd_al_shrink() - Removes all active extents form the activity log
+ * @mdev:       DRBD device.
+ *
+ * Removes all active extents form the activity log, waiting until
+ * the reference count of each entry dropped to 0 first, of course.
+ *
+ * You need to lock mdev->act_log with lc_try_lock() / lc_unlock()
+ */
+void drbd_al_shrink(struct drbd_conf *mdev)
+{
+        struct lc_element *al_ext;
+        int i;
+
+        D_ASSERT(test_bit(__LC_DIRTY, &mdev->act_log->flags));
+
+        for (i = 0; i < mdev->act_log->nr_elements; i++) {
+                al_ext = lc_element_by_index(mdev->act_log, i);
+                if (al_ext->lc_number == LC_FREE)
+                        continue;
+                wait_event(mdev->al_wait, _try_lc_del(mdev, al_ext));
+        }
+
+        wake_up(&mdev->al_wait);
+}
+
+static int w_update_odbm(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct update_odbm_work *udw = container_of(w, struct update_odbm_work, w);
+
+        if (!get_ldev(mdev)) {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_warn(DEV, "Can not update on disk bitmap, local IO disabled.\n");
+                kfree(udw);
+                return 1;
+        }
+
+        drbd_bm_write_sect(mdev, udw->enr);
+        put_ldev(mdev);
+
+        kfree(udw);
+
+        if (drbd_bm_total_weight(mdev) <= mdev->rs_failed) {
+                switch (mdev->state.conn) {
+                case C_SYNC_SOURCE:  case C_SYNC_TARGET:
+                case C_PAUSED_SYNC_S: case C_PAUSED_SYNC_T:
+                        drbd_resync_finished(mdev);
+                default:
+                        /* nothing to do */
+                        break;
+                }
+        }
+        drbd_bcast_sync_progress(mdev);
+
+        return 1;
+}
+
+
+/* ATTENTION. The AL's extents are 4MB each, while the extents in the
+ * resync LRU-cache are 16MB each.
+ * The caller of this function has to hold an get_ldev() reference.
+ *
+ * TODO will be obsoleted once we have a caching lru of the on disk bitmap
+ */
+static void drbd_try_clear_on_disk_bm(struct drbd_conf *mdev, sector_t sector,
+                                      int count, int success)
+{
+        struct lc_element *e;
+        struct update_odbm_work *udw;
+
+        unsigned int enr;
+
+        D_ASSERT(atomic_read(&mdev->local_cnt));
+
+        /* I simply assume that a sector/size pair never crosses
+         * a 16 MB extent border. (Currently this is true...) */
+        enr = BM_SECT_TO_EXT(sector);
+
+        e = lc_get(mdev->resync, enr);
+        if (e) {
+                struct bm_extent *ext = lc_entry(e, struct bm_extent, lce);
+                if (ext->lce.lc_number == enr) {
+                        if (success)
+                                ext->rs_left -= count;
+                        else
+                                ext->rs_failed += count;
+                        if (ext->rs_left < ext->rs_failed) {
+                                dev_err(DEV, "BAD! sector=%llus enr=%u rs_left=%d "
+                                    "rs_failed=%d count=%d\n",
+                                     (unsigned long long)sector,
+                                     ext->lce.lc_number, ext->rs_left,
+                                     ext->rs_failed, count);
+                                dump_stack();
+
+                                lc_put(mdev->resync, &ext->lce);
+                                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                                return;
+                        }
+                } else {
+                        /* Normally this element should be in the cache,
+                         * since drbd_rs_begin_io() pulled it already in.
+                         *
+                         * But maybe an application write finished, and we set
+                         * something outside the resync lru_cache in sync.
+                         */
+                        int rs_left = drbd_bm_e_weight(mdev, enr);
+                        if (ext->flags != 0) {
+                                dev_warn(DEV, "changing resync lce: %d[%u;%02lx]"
+                                     " -> %d[%u;00]\n",
+                                     ext->lce.lc_number, ext->rs_left,
+                                     ext->flags, enr, rs_left);
+                                ext->flags = 0;
+                        }
+                        if (ext->rs_failed) {
+                                dev_warn(DEV, "Kicking resync_lru element enr=%u "
+                                     "out with rs_failed=%d\n",
+                                     ext->lce.lc_number, ext->rs_failed);
+                                set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+                        }
+                        ext->rs_left = rs_left;
+                        ext->rs_failed = success ? 0 : count;
+                        lc_changed(mdev->resync, &ext->lce);
+                }
+                lc_put(mdev->resync, &ext->lce);
+                /* no race, we are within the al_lock! */
+
+                if (ext->rs_left == ext->rs_failed) {
+                        ext->rs_failed = 0;
+
+                        udw = kmalloc(sizeof(*udw), GFP_ATOMIC);
+                        if (udw) {
+                                udw->enr = ext->lce.lc_number;
+                                udw->w.cb = w_update_odbm;
+                                drbd_queue_work_front(&mdev->data.work, &udw->w);
+                        } else {
+                                dev_warn(DEV, "Could not kmalloc an udw\n");
+                                set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+                        }
+                }
+        } else {
+                dev_err(DEV, "lc_get() failed! locked=%d/%d flags=%lu\n",
+                    mdev->resync_locked,
+                    mdev->resync->nr_elements,
+                    mdev->resync->flags);
+        }
+}
+
+/* clear the bit corresponding to the piece of storage in question:
+ * size byte of data starting from sector.  Only clear a bits of the affected
+ * one ore more _aligned_ BM_BLOCK_SIZE blocks.
+ *
+ * called by worker on C_SYNC_TARGET and receiver on SyncSource.
+ *
+ */
+void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector, int size,
+                       const char *file, const unsigned int line)
+{
+        /* Is called from worker and receiver context _only_ */
+        unsigned long sbnr, ebnr, lbnr;
+        unsigned long count = 0;
+        sector_t esector, nr_sectors;
+        int wake_up = 0;
+        unsigned long flags;
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "drbd_set_in_sync: sector=%llus size=%d nonsense!\n",
+                                (unsigned long long)sector, size);
+                return;
+        }
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors) return;
+        ERR_IF(esector >= nr_sectors) esector = (nr_sectors-1);
+
+        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+        /* we clear it (in sync).
+         * round up start sector, round down end sector.  we make sure we only
+         * clear full, aligned, BM_BLOCK_SIZE (4K) blocks */
+        if (unlikely(esector < BM_SECT_PER_BIT-1))
+                return;
+        if (unlikely(esector == (nr_sectors-1)))
+                ebnr = lbnr;
+        else
+                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+                          "drbd_set_in_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+                          (unsigned long long)sector, size, sbnr, ebnr);
+
+        if (sbnr > ebnr)
+                return;
+
+        /*
+         * ok, (capacity & 7) != 0 sometimes, but who cares...
+         * we count rs_{total,left} in bits, not sectors.
+         */
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        count = drbd_bm_clear_bits(mdev, sbnr, ebnr);
+        if (count) {
+                /* we need the lock for drbd_try_clear_on_disk_bm */
+                if (jiffies - mdev->rs_mark_time > HZ*10) {
+                        /* should be rolling marks,
+                         * but we estimate only anyways. */
+                        if (mdev->rs_mark_left != drbd_bm_total_weight(mdev) &&
+                            mdev->state.conn != C_PAUSED_SYNC_T &&
+                            mdev->state.conn != C_PAUSED_SYNC_S) {
+                                mdev->rs_mark_time = jiffies;
+                                mdev->rs_mark_left = drbd_bm_total_weight(mdev);
+                        }
+                }
+                if (get_ldev(mdev)) {
+                        drbd_try_clear_on_disk_bm(mdev, sector, count, TRUE);
+                        put_ldev(mdev);
+                }
+                /* just wake_up unconditional now, various lc_chaged(),
+                 * lc_put() in drbd_try_clear_on_disk_bm(). */
+                wake_up = 1;
+        }
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+        if (wake_up)
+                wake_up(&mdev->al_wait);
+}
+
+/*
+ * this is intended to set one request worth of data out of sync.
+ * affects at least 1 bit,
+ * and at most 1+DRBD_MAX_SEGMENT_SIZE/BM_BLOCK_SIZE bits.
+ *
+ * called by tl_clear and drbd_send_dblock (==drbd_make_request).
+ * so this can be _any_ process.
+ */
+void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector, int size,
+                            const char *file, const unsigned int line)
+{
+        unsigned long sbnr, ebnr, lbnr, flags;
+        sector_t esector, nr_sectors;
+        unsigned int enr, count;
+        struct lc_element *e;
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "sector: %llus, size: %d\n",
+                        (unsigned long long)sector, size);
+                return;
+        }
+
+        if (!get_ldev(mdev))
+                return; /* no disk, no metadata, no bitmap to set bits in */
+
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors)
+                goto out;
+        ERR_IF(esector >= nr_sectors)
+                esector = (nr_sectors-1);
+
+        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+        /* we set it out of sync,
+         * we do not need to round anything here */
+        sbnr = BM_SECT_TO_BIT(sector);
+        ebnr = BM_SECT_TO_BIT(esector);
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS,
+                          "drbd_set_out_of_sync: sector=%llus size=%u sbnr=%lu ebnr=%lu\n",
+                          (unsigned long long)sector, size, sbnr, ebnr);
+
+        /* ok, (capacity & 7) != 0 sometimes, but who cares...
+         * we count rs_{total,left} in bits, not sectors.  */
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        count = drbd_bm_set_bits(mdev, sbnr, ebnr);
+
+        enr = BM_SECT_TO_EXT(sector);
+        e = lc_find(mdev->resync, enr);
+        if (e)
+                lc_entry(e, struct bm_extent, lce)->rs_left += count;
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+
+out:
+        put_ldev(mdev);
+}
+
+static
+struct bm_extent *_bme_get(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int wakeup = 0;
+        unsigned long rs_flags;
+
+        spin_lock_irq(&mdev->al_lock);
+        if (mdev->resync_locked > mdev->resync->nr_elements/2) {
+                spin_unlock_irq(&mdev->al_lock);
+                return NULL;
+        }
+        e = lc_get(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (bm_ext) {
+                if (bm_ext->lce.lc_number != enr) {
+                        bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+                        bm_ext->rs_failed = 0;
+                        lc_changed(mdev->resync, &bm_ext->lce);
+                        wakeup = 1;
+                }
+                if (bm_ext->lce.refcnt == 1)
+                        mdev->resync_locked++;
+                set_bit(BME_NO_WRITES, &bm_ext->flags);
+        }
+        rs_flags = mdev->resync->flags;
+        spin_unlock_irq(&mdev->al_lock);
+        if (wakeup)
+                wake_up(&mdev->al_wait);
+
+        if (!bm_ext) {
+                if (rs_flags & LC_STARVING)
+                        dev_warn(DEV, "Have to wait for element"
+                             " (resync LRU too small?)\n");
+                BUG_ON(rs_flags & LC_DIRTY);
+        }
+
+        return bm_ext;
+}
+
+static int _is_in_al(struct drbd_conf *mdev, unsigned int enr)
+{
+        struct lc_element *al_ext;
+        int rv = 0;
+
+        spin_lock_irq(&mdev->al_lock);
+        if (unlikely(enr == mdev->act_log->new_number))
+                rv = 1;
+        else {
+                al_ext = lc_find(mdev->act_log, enr);
+                if (al_ext) {
+                        if (al_ext->refcnt)
+                                rv = 1;
+                }
+        }
+        spin_unlock_irq(&mdev->al_lock);
+
+        /*
+        if (unlikely(rv)) {
+                dev_info(DEV, "Delaying sync read until app's write is done\n");
+        }
+        */
+        return rv;
+}
+
+/**
+ * drbd_rs_begin_io() - Gets an extent in the resync LRU cache and sets it to BME_LOCKED
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ *
+ * This functions sleeps on al_wait. Returns 1 on success, 0 if interrupted.
+ */
+int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        struct bm_extent *bm_ext;
+        int i, sig;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                          "drbd_rs_begin_io: sector=%llus (rs_end=%d)\n",
+                          (unsigned long long)sector, enr);
+
+        sig = wait_event_interruptible(mdev->al_wait,
+                        (bm_ext = _bme_get(mdev, enr)));
+        if (sig)
+                return 0;
+
+        if (test_bit(BME_LOCKED, &bm_ext->flags))
+                return 1;
+
+        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+                sig = wait_event_interruptible(mdev->al_wait,
+                                !_is_in_al(mdev, enr * AL_EXT_PER_BM_SECT + i));
+                if (sig) {
+                        spin_lock_irq(&mdev->al_lock);
+                        if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+                                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                                mdev->resync_locked--;
+                                wake_up(&mdev->al_wait);
+                        }
+                        spin_unlock_irq(&mdev->al_lock);
+                        return 0;
+                }
+        }
+
+        set_bit(BME_LOCKED, &bm_ext->flags);
+
+        return 1;
+}
+
+/**
+ * drbd_try_rs_begin_io() - Gets an extent in the resync LRU cache, does not sleep
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ *
+ * Gets an extent in the resync LRU cache, sets it to BME_NO_WRITES, then
+ * tries to set it to BME_LOCKED. Returns 0 upon success, and -EAGAIN
+ * if there is still application IO going on in this area.
+ */
+int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        const unsigned int al_enr = enr*AL_EXT_PER_BM_SECT;
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int i;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "drbd_try_rs_begin_io: sector=%llus\n",
+                          (unsigned long long)sector);
+
+        spin_lock_irq(&mdev->al_lock);
+        if (mdev->resync_wenr != LC_FREE && mdev->resync_wenr != enr) {
+                /* in case you have very heavy scattered io, it may
+                 * stall the syncer undefined if we give up the ref count
+                 * when we try again and requeue.
+                 *
+                 * if we don't give up the refcount, but the next time
+                 * we are scheduled this extent has been "synced" by new
+                 * application writes, we'd miss the lc_put on the
+                 * extent we keep the refcount on.
+                 * so we remembered which extent we had to try again, and
+                 * if the next requested one is something else, we do
+                 * the lc_put here...
+                 * we also have to wake_up
+                 */
+
+                trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                  "dropping %u, apparently got 'synced' by application io\n",
+                                  mdev->resync_wenr);
+
+                e = lc_find(mdev->resync, mdev->resync_wenr);
+                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                if (bm_ext) {
+                        D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                        D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+                        clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                        mdev->resync_wenr = LC_FREE;
+                        if (lc_put(mdev->resync, &bm_ext->lce) == 0)
+                                mdev->resync_locked--;
+                        wake_up(&mdev->al_wait);
+                } else {
+                        dev_alert(DEV, "LOGIC BUG\n");
+                }
+        }
+        /* TRY. */
+        e = lc_try_get(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (bm_ext) {
+                if (test_bit(BME_LOCKED, &bm_ext->flags))
+                        goto proceed;
+                if (!test_and_set_bit(BME_NO_WRITES, &bm_ext->flags)) {
+                        mdev->resync_locked++;
+                } else {
+                        /* we did set the BME_NO_WRITES,
+                         * but then could not set BME_LOCKED,
+                         * so we tried again.
+                         * drop the extra reference. */
+                        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                          "dropping extra reference on %u\n", enr);
+
+                        bm_ext->lce.refcnt--;
+                        D_ASSERT(bm_ext->lce.refcnt > 0);
+                }
+                goto check_al;
+        } else {
+                /* do we rather want to try later? */
+                if (mdev->resync_locked > mdev->resync->nr_elements-3) {
+                        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                                          "resync_locked = %u!\n", mdev->resync_locked);
+
+                        goto try_again;
+                }
+                /* Do or do not. There is no try. -- Yoda */
+                e = lc_get(mdev->resync, enr);
+                bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                if (!bm_ext) {
+                        const unsigned long rs_flags = mdev->resync->flags;
+                        if (rs_flags & LC_STARVING)
+                                dev_warn(DEV, "Have to wait for element"
+                                     " (resync LRU too small?)\n");
+                        BUG_ON(rs_flags & LC_DIRTY);
+                        goto try_again;
+                }
+                if (bm_ext->lce.lc_number != enr) {
+                        bm_ext->rs_left = drbd_bm_e_weight(mdev, enr);
+                        bm_ext->rs_failed = 0;
+                        lc_changed(mdev->resync, &bm_ext->lce);
+                        wake_up(&mdev->al_wait);
+                        D_ASSERT(test_bit(BME_LOCKED, &bm_ext->flags) == 0);
+                }
+                set_bit(BME_NO_WRITES, &bm_ext->flags);
+                D_ASSERT(bm_ext->lce.refcnt == 1);
+                mdev->resync_locked++;
+                goto check_al;
+        }
+check_al:
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "checking al for %u\n", enr);
+
+        for (i = 0; i < AL_EXT_PER_BM_SECT; i++) {
+                if (unlikely(al_enr+i == mdev->act_log->new_number))
+                        goto try_again;
+                if (lc_is_used(mdev->act_log, al_enr+i))
+                        goto try_again;
+        }
+        set_bit(BME_LOCKED, &bm_ext->flags);
+proceed:
+        mdev->resync_wenr = LC_FREE;
+        spin_unlock_irq(&mdev->al_lock);
+        return 0;
+
+try_again:
+        trace_drbd_resync(mdev, TRACE_LVL_ALL, "need to try again for %u\n", enr);
+        if (bm_ext)
+                mdev->resync_wenr = enr;
+        spin_unlock_irq(&mdev->al_lock);
+        return -EAGAIN;
+}
+
+void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector)
+{
+        unsigned int enr = BM_SECT_TO_EXT(sector);
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        unsigned long flags;
+
+        trace_drbd_resync(mdev, TRACE_LVL_ALL,
+                          "drbd_rs_complete_io: sector=%llus (rs_enr=%d)\n",
+                          (long long)sector, enr);
+
+        spin_lock_irqsave(&mdev->al_lock, flags);
+        e = lc_find(mdev->resync, enr);
+        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+        if (!bm_ext) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "drbd_rs_complete_io() called, but extent not found\n");
+                return;
+        }
+
+        if (bm_ext->lce.refcnt == 0) {
+                spin_unlock_irqrestore(&mdev->al_lock, flags);
+                dev_err(DEV, "drbd_rs_complete_io(,%llu [=%u]) called, "
+                    "but refcnt is 0!?\n",
+                    (unsigned long long)sector, enr);
+                return;
+        }
+
+        if (lc_put(mdev->resync, &bm_ext->lce) == 0) {
+                clear_bit(BME_LOCKED, &bm_ext->flags);
+                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                mdev->resync_locked--;
+                wake_up(&mdev->al_wait);
+        }
+
+        spin_unlock_irqrestore(&mdev->al_lock, flags);
+}
+
+/**
+ * drbd_rs_cancel_all() - Removes all extents from the resync LRU (even BME_LOCKED)
+ * @mdev:       DRBD device.
+ */
+void drbd_rs_cancel_all(struct drbd_conf *mdev)
+{
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_cancel_all\n");
+
+        spin_lock_irq(&mdev->al_lock);
+
+        if (get_ldev_if_state(mdev, D_FAILED)) { /* Makes sure ->resync is there. */
+                lc_reset(mdev->resync);
+                put_ldev(mdev);
+        }
+        mdev->resync_locked = 0;
+        mdev->resync_wenr = LC_FREE;
+        spin_unlock_irq(&mdev->al_lock);
+        wake_up(&mdev->al_wait);
+}
+
+/**
+ * drbd_rs_del_all() - Gracefully remove all extents from the resync LRU
+ * @mdev:       DRBD device.
+ *
+ * Returns 0 upon success, -EAGAIN if at least one reference count was
+ * not zero.
+ */
+int drbd_rs_del_all(struct drbd_conf *mdev)
+{
+        struct lc_element *e;
+        struct bm_extent *bm_ext;
+        int i;
+
+        trace_drbd_resync(mdev, TRACE_LVL_METRICS, "drbd_rs_del_all\n");
+
+        spin_lock_irq(&mdev->al_lock);
+
+        if (get_ldev_if_state(mdev, D_FAILED)) {
+                /* ok, ->resync is there. */
+                for (i = 0; i < mdev->resync->nr_elements; i++) {
+                        e = lc_element_by_index(mdev->resync, i);
+                        bm_ext = e ? lc_entry(e, struct bm_extent, lce) : NULL;
+                        if (bm_ext->lce.lc_number == LC_FREE)
+                                continue;
+                        if (bm_ext->lce.lc_number == mdev->resync_wenr) {
+                                dev_info(DEV, "dropping %u in drbd_rs_del_all, apparently"
+                                     " got 'synced' by application io\n",
+                                     mdev->resync_wenr);
+                                D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                                D_ASSERT(test_bit(BME_NO_WRITES, &bm_ext->flags));
+                                clear_bit(BME_NO_WRITES, &bm_ext->flags);
+                                mdev->resync_wenr = LC_FREE;
+                                lc_put(mdev->resync, &bm_ext->lce);
+                        }
+                        if (bm_ext->lce.refcnt != 0) {
+                                dev_info(DEV, "Retrying drbd_rs_del_all() later. "
+                                     "refcnt=%d\n", bm_ext->lce.refcnt);
+                                put_ldev(mdev);
+                                spin_unlock_irq(&mdev->al_lock);
+                                return -EAGAIN;
+                        }
+                        D_ASSERT(!test_bit(BME_LOCKED, &bm_ext->flags));
+                        D_ASSERT(!test_bit(BME_NO_WRITES, &bm_ext->flags));
+                        lc_del(mdev->resync, &bm_ext->lce);
+                }
+                D_ASSERT(mdev->resync->used == 0);
+                put_ldev(mdev);
+        }
+        spin_unlock_irq(&mdev->al_lock);
+
+        return 0;
+}
+
+/**
+ * drbd_rs_failed_io() - Record information on a failure to resync the specified blocks
+ * @mdev:       DRBD device.
+ * @sector:     The sector number.
+ * @size:       Size of failed IO operation, in byte.
+ */
+void drbd_rs_failed_io(struct drbd_conf *mdev, sector_t sector, int size)
+{
+        /* Is called from worker and receiver context _only_ */
+        unsigned long sbnr, ebnr, lbnr;
+        unsigned long count;
+        sector_t esector, nr_sectors;
+        int wake_up = 0;
+
+        trace_drbd_resync(mdev, TRACE_LVL_SUMMARY,
+                          "drbd_rs_failed_io: sector=%llus, size=%u\n",
+                          (unsigned long long)sector, size);
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "drbd_rs_failed_io: sector=%llus size=%d nonsense!\n",
+                                (unsigned long long)sector, size);
+                return;
+        }
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        ERR_IF(sector >= nr_sectors) return;
+        ERR_IF(esector >= nr_sectors) esector = (nr_sectors-1);
+
+        lbnr = BM_SECT_TO_BIT(nr_sectors-1);
+
+        /*
+         * round up start sector, round down end sector.  we make sure we only
+         * handle full, aligned, BM_BLOCK_SIZE (4K) blocks */
+        if (unlikely(esector < BM_SECT_PER_BIT-1))
+                return;
+        if (unlikely(esector == (nr_sectors-1)))
+                ebnr = lbnr;
+        else
+                ebnr = BM_SECT_TO_BIT(esector - (BM_SECT_PER_BIT-1));
+        sbnr = BM_SECT_TO_BIT(sector + BM_SECT_PER_BIT-1);
+
+        if (sbnr > ebnr)
+                return;
+
+        /*
+         * ok, (capacity & 7) != 0 sometimes, but who cares...
+         * we count rs_{total,left} in bits, not sectors.
+         */
+        spin_lock_irq(&mdev->al_lock);
+        count = drbd_bm_count_bits(mdev, sbnr, ebnr);
+        if (count) {
+                mdev->rs_failed += count;
+
+                if (get_ldev(mdev)) {
+                        drbd_try_clear_on_disk_bm(mdev, sector, count, FALSE);
+                        put_ldev(mdev);
+                }
+
+                /* just wake_up unconditional now, various lc_chaged(),
+                 * lc_put() in drbd_try_clear_on_disk_bm(). */
+                wake_up = 1;
+        }
+        spin_unlock_irq(&mdev->al_lock);
+        if (wake_up)
+                wake_up(&mdev->al_wait);
+}
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
new file mode 100644
index 000000000000..b61057e77882
--- /dev/null
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -0,0 +1,1327 @@
+/*
+   drbd_bitmap.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2004-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2004-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2004-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/bitops.h>
+#include <linux/vmalloc.h>
+#include <linux/string.h>
+#include <linux/drbd.h>
+#include <asm/kmap_types.h>
+#include "drbd_int.h"
+
+/* OPAQUE outside this file!
+ * interface defined in drbd_int.h
+
+ * convention:
+ * function name drbd_bm_... => used elsewhere, "public".
+ * function name      bm_... => internal to implementation, "private".
+
+ * Note that since find_first_bit returns int, at the current granularity of
+ * the bitmap (4KB per byte), this implementation "only" supports up to
+ * 1<<(32+12) == 16 TB...
+ */
+
+/*
+ * NOTE
+ *  Access to the *bm_pages is protected by bm_lock.
+ *  It is safe to read the other members within the lock.
+ *
+ *  drbd_bm_set_bits is called from bio_endio callbacks,
+ *  We may be called with irq already disabled,
+ *  so we need spin_lock_irqsave().
+ *  And we need the kmap_atomic.
+ */
+struct drbd_bitmap {
+        struct page **bm_pages;
+        spinlock_t bm_lock;
+        /* WARNING unsigned long bm_*:
+         * 32bit number of bit offset is just enough for 512 MB bitmap.
+         * it will blow up if we make the bitmap bigger...
+         * not that it makes much sense to have a bitmap that large,
+         * rather change the granularity to 16k or 64k or something.
+         * (that implies other problems, however...)
+         */
+        unsigned long bm_set;       /* nr of set bits; THINK maybe atomic_t? */
+        unsigned long bm_bits;
+        size_t   bm_words;
+        size_t   bm_number_of_pages;
+        sector_t bm_dev_capacity;
+        struct semaphore bm_change; /* serializes resize operations */
+
+        atomic_t bm_async_io;
+        wait_queue_head_t bm_io_wait;
+
+        unsigned long  bm_flags;
+
+        /* debugging aid, in case we are still racy somewhere */
+        char          *bm_why;
+        struct task_struct *bm_task;
+};
+
+/* definition of bits in bm_flags */
+#define BM_LOCKED       0
+#define BM_MD_IO_ERROR  1
+#define BM_P_VMALLOCED  2
+
+static int bm_is_locked(struct drbd_bitmap *b)
+{
+        return test_bit(BM_LOCKED, &b->bm_flags);
+}
+
+#define bm_print_lock_info(m) __bm_print_lock_info(m, __func__)
+static void __bm_print_lock_info(struct drbd_conf *mdev, const char *func)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        if (!__ratelimit(&drbd_ratelimit_state))
+                return;
+        dev_err(DEV, "FIXME %s in %s, bitmap locked for '%s' by %s\n",
+            current == mdev->receiver.task ? "receiver" :
+            current == mdev->asender.task  ? "asender"  :
+            current == mdev->worker.task   ? "worker"   : current->comm,
+            func, b->bm_why ?: "?",
+            b->bm_task == mdev->receiver.task ? "receiver" :
+            b->bm_task == mdev->asender.task  ? "asender"  :
+            b->bm_task == mdev->worker.task   ? "worker"   : "?");
+}
+
+void drbd_bm_lock(struct drbd_conf *mdev, char *why)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        int trylock_failed;
+
+        if (!b) {
+                dev_err(DEV, "FIXME no bitmap in drbd_bm_lock!?\n");
+                return;
+        }
+
+        trylock_failed = down_trylock(&b->bm_change);
+
+        if (trylock_failed) {
+                dev_warn(DEV, "%s going to '%s' but bitmap already locked for '%s' by %s\n",
+                    current == mdev->receiver.task ? "receiver" :
+                    current == mdev->asender.task  ? "asender"  :
+                    current == mdev->worker.task   ? "worker"   : current->comm,
+                    why, b->bm_why ?: "?",
+                    b->bm_task == mdev->receiver.task ? "receiver" :
+                    b->bm_task == mdev->asender.task  ? "asender"  :
+                    b->bm_task == mdev->worker.task   ? "worker"   : "?");
+                down(&b->bm_change);
+        }
+        if (__test_and_set_bit(BM_LOCKED, &b->bm_flags))
+                dev_err(DEV, "FIXME bitmap already locked in bm_lock\n");
+
+        b->bm_why  = why;
+        b->bm_task = current;
+}
+
+void drbd_bm_unlock(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        if (!b) {
+                dev_err(DEV, "FIXME no bitmap in drbd_bm_unlock!?\n");
+                return;
+        }
+
+        if (!__test_and_clear_bit(BM_LOCKED, &mdev->bitmap->bm_flags))
+                dev_err(DEV, "FIXME bitmap not locked in bm_unlock\n");
+
+        b->bm_why  = NULL;
+        b->bm_task = NULL;
+        up(&b->bm_change);
+}
+
+/* word offset to long pointer */
+static unsigned long *__bm_map_paddr(struct drbd_bitmap *b, unsigned long offset, const enum km_type km)
+{
+        struct page *page;
+        unsigned long page_nr;
+
+        /* page_nr = (word*sizeof(long)) >> PAGE_SHIFT; */
+        page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+        BUG_ON(page_nr >= b->bm_number_of_pages);
+        page = b->bm_pages[page_nr];
+
+        return (unsigned long *) kmap_atomic(page, km);
+}
+
+static unsigned long * bm_map_paddr(struct drbd_bitmap *b, unsigned long offset)
+{
+        return __bm_map_paddr(b, offset, KM_IRQ1);
+}
+
+static void __bm_unmap(unsigned long *p_addr, const enum km_type km)
+{
+        kunmap_atomic(p_addr, km);
+};
+
+static void bm_unmap(unsigned long *p_addr)
+{
+        return __bm_unmap(p_addr, KM_IRQ1);
+}
+
+/* long word offset of _bitmap_ sector */
+#define S2W(s)  ((s)<<(BM_EXT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+/* word offset from start of bitmap to word number _in_page_
+ * modulo longs per page
+#define MLPP(X) ((X) % (PAGE_SIZE/sizeof(long))
+ hm, well, Philipp thinks gcc might not optimze the % into & (... - 1)
+ so do it explicitly:
+ */
+#define MLPP(X) ((X) & ((PAGE_SIZE/sizeof(long))-1))
+
+/* Long words per page */
+#define LWPP (PAGE_SIZE/sizeof(long))
+
+/*
+ * actually most functions herein should take a struct drbd_bitmap*, not a
+ * struct drbd_conf*, but for the debug macros I like to have the mdev around
+ * to be able to report device specific.
+ */
+
+static void bm_free_pages(struct page **pages, unsigned long number)
+{
+        unsigned long i;
+        if (!pages)
+                return;
+
+        for (i = 0; i < number; i++) {
+                if (!pages[i]) {
+                        printk(KERN_ALERT "drbd: bm_free_pages tried to free "
+                                          "a NULL pointer; i=%lu n=%lu\n",
+                                          i, number);
+                        continue;
+                }
+                __free_page(pages[i]);
+                pages[i] = NULL;
+        }
+}
+
+static void bm_vk_free(void *ptr, int v)
+{
+        if (v)
+                vfree(ptr);
+        else
+                kfree(ptr);
+}
+
+/*
+ * "have" and "want" are NUMBER OF PAGES.
+ */
+static struct page **bm_realloc_pages(struct drbd_bitmap *b, unsigned long want)
+{
+        struct page **old_pages = b->bm_pages;
+        struct page **new_pages, *page;
+        unsigned int i, bytes, vmalloced = 0;
+        unsigned long have = b->bm_number_of_pages;
+
+        BUG_ON(have == 0 && old_pages != NULL);
+        BUG_ON(have != 0 && old_pages == NULL);
+
+        if (have == want)
+                return old_pages;
+
+        /* Trying kmalloc first, falling back to vmalloc.
+         * GFP_KERNEL is ok, as this is done when a lower level disk is
+         * "attached" to the drbd.  Context is receiver thread or cqueue
+         * thread.  As we have no disk yet, we are not in the IO path,
+         * not even the IO path of the peer. */
+        bytes = sizeof(struct page *)*want;
+        new_pages = kmalloc(bytes, GFP_KERNEL);
+        if (!new_pages) {
+                new_pages = vmalloc(bytes);
+                if (!new_pages)
+                        return NULL;
+                vmalloced = 1;
+        }
+
+        memset(new_pages, 0, bytes);
+        if (want >= have) {
+                for (i = 0; i < have; i++)
+                        new_pages[i] = old_pages[i];
+                for (; i < want; i++) {
+                        page = alloc_page(GFP_HIGHUSER);
+                        if (!page) {
+                                bm_free_pages(new_pages + have, i - have);
+                                bm_vk_free(new_pages, vmalloced);
+                                return NULL;
+                        }
+                        new_pages[i] = page;
+                }
+        } else {
+                for (i = 0; i < want; i++)
+                        new_pages[i] = old_pages[i];
+                /* NOT HERE, we are outside the spinlock!
+                bm_free_pages(old_pages + want, have - want);
+                */
+        }
+
+        if (vmalloced)
+                set_bit(BM_P_VMALLOCED, &b->bm_flags);
+        else
+                clear_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+        return new_pages;
+}
+
+/*
+ * called on driver init only. TODO call when a device is created.
+ * allocates the drbd_bitmap, and stores it in mdev->bitmap.
+ */
+int drbd_bm_init(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        WARN_ON(b != NULL);
+        b = kzalloc(sizeof(struct drbd_bitmap), GFP_KERNEL);
+        if (!b)
+                return -ENOMEM;
+        spin_lock_init(&b->bm_lock);
+        init_MUTEX(&b->bm_change);
+        init_waitqueue_head(&b->bm_io_wait);
+
+        mdev->bitmap = b;
+
+        return 0;
+}
+
+sector_t drbd_bm_capacity(struct drbd_conf *mdev)
+{
+        ERR_IF(!mdev->bitmap) return 0;
+        return mdev->bitmap->bm_dev_capacity;
+}
+
+/* called on driver unload. TODO: call when a device is destroyed.
+ */
+void drbd_bm_cleanup(struct drbd_conf *mdev)
+{
+        ERR_IF (!mdev->bitmap) return;
+        bm_free_pages(mdev->bitmap->bm_pages, mdev->bitmap->bm_number_of_pages);
+        bm_vk_free(mdev->bitmap->bm_pages, test_bit(BM_P_VMALLOCED, &mdev->bitmap->bm_flags));
+        kfree(mdev->bitmap);
+        mdev->bitmap = NULL;
+}
+
+/*
+ * since (b->bm_bits % BITS_PER_LONG) != 0,
+ * this masks out the remaining bits.
+ * Returns the number of bits cleared.
+ */
+static int bm_clear_surplus(struct drbd_bitmap *b)
+{
+        const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+        size_t w = b->bm_bits >> LN2_BPL;
+        int cleared = 0;
+        unsigned long *p_addr, *bm;
+
+        p_addr = bm_map_paddr(b, w);
+        bm = p_addr + MLPP(w);
+        if (w < b->bm_words) {
+                cleared = hweight_long(*bm & ~mask);
+                *bm &= mask;
+                w++; bm++;
+        }
+
+        if (w < b->bm_words) {
+                cleared += hweight_long(*bm);
+                *bm = 0;
+        }
+        bm_unmap(p_addr);
+        return cleared;
+}
+
+static void bm_set_surplus(struct drbd_bitmap *b)
+{
+        const unsigned long mask = (1UL << (b->bm_bits & (BITS_PER_LONG-1))) - 1;
+        size_t w = b->bm_bits >> LN2_BPL;
+        unsigned long *p_addr, *bm;
+
+        p_addr = bm_map_paddr(b, w);
+        bm = p_addr + MLPP(w);
+        if (w < b->bm_words) {
+                *bm |= ~mask;
+                bm++; w++;
+        }
+
+        if (w < b->bm_words) {
+                *bm = ~(0UL);
+        }
+        bm_unmap(p_addr);
+}
+
+static unsigned long __bm_count_bits(struct drbd_bitmap *b, const int swap_endian)
+{
+        unsigned long *p_addr, *bm, offset = 0;
+        unsigned long bits = 0;
+        unsigned long i, do_now;
+
+        while (offset < b->bm_words) {
+                i = do_now = min_t(size_t, b->bm_words-offset, LWPP);
+                p_addr = __bm_map_paddr(b, offset, KM_USER0);
+                bm = p_addr + MLPP(offset);
+                while (i--) {
+#ifndef __LITTLE_ENDIAN
+                        if (swap_endian)
+                                *bm = lel_to_cpu(*bm);
+#endif
+                        bits += hweight_long(*bm++);
+                }
+                __bm_unmap(p_addr, KM_USER0);
+                offset += do_now;
+                cond_resched();
+        }
+
+        return bits;
+}
+
+static unsigned long bm_count_bits(struct drbd_bitmap *b)
+{
+        return __bm_count_bits(b, 0);
+}
+
+static unsigned long bm_count_bits_swap_endian(struct drbd_bitmap *b)
+{
+        return __bm_count_bits(b, 1);
+}
+
+/* offset and len in long words.*/
+static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
+{
+        unsigned long *p_addr, *bm;
+        size_t do_now, end;
+
+#define BM_SECTORS_PER_BIT (BM_BLOCK_SIZE/512)
+
+        end = offset + len;
+
+        if (end > b->bm_words) {
+                printk(KERN_ALERT "drbd: bm_memset end > bm_words\n");
+                return;
+        }
+
+        while (offset < end) {
+                do_now = min_t(size_t, ALIGN(offset + 1, LWPP), end) - offset;
+                p_addr = bm_map_paddr(b, offset);
+                bm = p_addr + MLPP(offset);
+                if (bm+do_now > p_addr + LWPP) {
+                        printk(KERN_ALERT "drbd: BUG BUG BUG! p_addr:%p bm:%p do_now:%d\n",
+                               p_addr, bm, (int)do_now);
+                        break; /* breaks to after catch_oob_access_end() only! */
+                }
+                memset(bm, c, do_now * sizeof(long));
+                bm_unmap(p_addr);
+                offset += do_now;
+        }
+}
+
+/*
+ * make sure the bitmap has enough room for the attached storage,
+ * if necessary, resize.
+ * called whenever we may have changed the device size.
+ * returns -ENOMEM if we could not allocate enough memory, 0 on success.
+ * In case this is actually a resize, we copy the old bitmap into the new one.
+ * Otherwise, the bitmap is initialized to all bits set.
+ */
+int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long bits, words, owords, obits, *p_addr, *bm;
+        unsigned long want, have, onpages; /* number of pages */
+        struct page **npages, **opages = NULL;
+        int err = 0, growing;
+        int opages_vmalloced;
+
+        ERR_IF(!b) return -ENOMEM;
+
+        drbd_bm_lock(mdev, "resize");
+
+        dev_info(DEV, "drbd_bm_resize called with capacity == %llu\n",
+                        (unsigned long long)capacity);
+
+        if (capacity == b->bm_dev_capacity)
+                goto out;
+
+        opages_vmalloced = test_bit(BM_P_VMALLOCED, &b->bm_flags);
+
+        if (capacity == 0) {
+                spin_lock_irq(&b->bm_lock);
+                opages = b->bm_pages;
+                onpages = b->bm_number_of_pages;
+                owords = b->bm_words;
+                b->bm_pages = NULL;
+                b->bm_number_of_pages =
+                b->bm_set   =
+                b->bm_bits  =
+                b->bm_words =
+                b->bm_dev_capacity = 0;
+                spin_unlock_irq(&b->bm_lock);
+                bm_free_pages(opages, onpages);
+                bm_vk_free(opages, opages_vmalloced);
+                goto out;
+        }
+        bits  = BM_SECT_TO_BIT(ALIGN(capacity, BM_SECT_PER_BIT));
+
+        /* if we would use
+           words = ALIGN(bits,BITS_PER_LONG) >> LN2_BPL;
+           a 32bit host could present the wrong number of words
+           to a 64bit host.
+        */
+        words = ALIGN(bits, 64) >> LN2_BPL;
+
+        if (get_ldev(mdev)) {
+                D_ASSERT((u64)bits <= (((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12));
+                put_ldev(mdev);
+        }
+
+        /* one extra long to catch off by one errors */
+        want = ALIGN((words+1)*sizeof(long), PAGE_SIZE) >> PAGE_SHIFT;
+        have = b->bm_number_of_pages;
+        if (want == have) {
+                D_ASSERT(b->bm_pages != NULL);
+                npages = b->bm_pages;
+        } else {
+                if (FAULT_ACTIVE(mdev, DRBD_FAULT_BM_ALLOC))
+                        npages = NULL;
+                else
+                        npages = bm_realloc_pages(b, want);
+        }
+
+        if (!npages) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        spin_lock_irq(&b->bm_lock);
+        opages = b->bm_pages;
+        owords = b->bm_words;
+        obits  = b->bm_bits;
+
+        growing = bits > obits;
+        if (opages)
+                bm_set_surplus(b);
+
+        b->bm_pages = npages;
+        b->bm_number_of_pages = want;
+        b->bm_bits  = bits;
+        b->bm_words = words;
+        b->bm_dev_capacity = capacity;
+
+        if (growing) {
+                bm_memset(b, owords, 0xff, words-owords);
+                b->bm_set += bits - obits;
+        }
+
+        if (want < have) {
+                /* implicit: (opages != NULL) && (opages != npages) */
+                bm_free_pages(opages + want, have - want);
+        }
+
+        p_addr = bm_map_paddr(b, words);
+        bm = p_addr + MLPP(words);
+        *bm = DRBD_MAGIC;
+        bm_unmap(p_addr);
+
+        (void)bm_clear_surplus(b);
+
+        spin_unlock_irq(&b->bm_lock);
+        if (opages != npages)
+                bm_vk_free(opages, opages_vmalloced);
+        if (!growing)
+                b->bm_set = bm_count_bits(b);
+        dev_info(DEV, "resync bitmap: bits=%lu words=%lu\n", bits, words);
+
+ out:
+        drbd_bm_unlock(mdev);
+        return err;
+}
+
+/* inherently racy:
+ * if not protected by other means, return value may be out of date when
+ * leaving this function...
+ * we still need to lock it, since it is important that this returns
+ * bm_set == 0 precisely.
+ *
+ * maybe bm_set should be atomic_t ?
+ */
+static unsigned long _drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long s;
+        unsigned long flags;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        s = b->bm_set;
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+
+        return s;
+}
+
+unsigned long drbd_bm_total_weight(struct drbd_conf *mdev)
+{
+        unsigned long s;
+        /* if I don't have a disk, I don't know about out-of-sync status */
+        if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+                return 0;
+        s = _drbd_bm_total_weight(mdev);
+        put_ldev(mdev);
+        return s;
+}
+
+size_t drbd_bm_words(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        return b->bm_words;
+}
+
+unsigned long drbd_bm_bits(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return 0;
+
+        return b->bm_bits;
+}
+
+/* merge number words from buffer into the bitmap starting at offset.
+ * buffer[i] is expected to be little endian unsigned long.
+ * bitmap must be locked by drbd_bm_lock.
+ * currently only used from receive_bitmap.
+ */
+void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+                        unsigned long *buffer)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr, *bm;
+        unsigned long word, bits;
+        size_t end, do_now;
+
+        end = offset + number;
+
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+        if (number == 0)
+                return;
+        WARN_ON(offset >= b->bm_words);
+        WARN_ON(end    >  b->bm_words);
+
+        spin_lock_irq(&b->bm_lock);
+        while (offset < end) {
+                do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+                p_addr = bm_map_paddr(b, offset);
+                bm = p_addr + MLPP(offset);
+                offset += do_now;
+                while (do_now--) {
+                        bits = hweight_long(*bm);
+                        word = *bm | lel_to_cpu(*buffer++);
+                        *bm++ = word;
+                        b->bm_set += hweight_long(word) - bits;
+                }
+                bm_unmap(p_addr);
+        }
+        /* with 32bit <-> 64bit cross-platform connect
+         * this is only correct for current usage,
+         * where we _know_ that we are 64 bit aligned,
+         * and know that this function is used in this way, too...
+         */
+        if (end == b->bm_words)
+                b->bm_set -= bm_clear_surplus(b);
+
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* copy number words from the bitmap starting at offset into the buffer.
+ * buffer[i] will be little endian unsigned long.
+ */
+void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset, size_t number,
+                     unsigned long *buffer)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr, *bm;
+        size_t end, do_now;
+
+        end = offset + number;
+
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        if ((offset >= b->bm_words) ||
+            (end    >  b->bm_words) ||
+            (number <= 0))
+                dev_err(DEV, "offset=%lu number=%lu bm_words=%lu\n",
+                        (unsigned long) offset,
+                        (unsigned long) number,
+                        (unsigned long) b->bm_words);
+        else {
+                while (offset < end) {
+                        do_now = min_t(size_t, ALIGN(offset+1, LWPP), end) - offset;
+                        p_addr = bm_map_paddr(b, offset);
+                        bm = p_addr + MLPP(offset);
+                        offset += do_now;
+                        while (do_now--)
+                                *buffer++ = cpu_to_lel(*bm++);
+                        bm_unmap(p_addr);
+                }
+        }
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* set all bits in the bitmap */
+void drbd_bm_set_all(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        bm_memset(b, 0, 0xff, b->bm_words);
+        (void)bm_clear_surplus(b);
+        b->bm_set = b->bm_bits;
+        spin_unlock_irq(&b->bm_lock);
+}
+
+/* clear all bits in the bitmap */
+void drbd_bm_clear_all(struct drbd_conf *mdev)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        ERR_IF(!b) return;
+        ERR_IF(!b->bm_pages) return;
+
+        spin_lock_irq(&b->bm_lock);
+        bm_memset(b, 0, 0, b->bm_words);
+        b->bm_set = 0;
+        spin_unlock_irq(&b->bm_lock);
+}
+
+static void bm_async_io_complete(struct bio *bio, int error)
+{
+        struct drbd_bitmap *b = bio->bi_private;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+
+        /* strange behavior of some lower level drivers...
+         * fail the request by clearing the uptodate flag,
+         * but do not return any error?!
+         * do we want to WARN() on this? */
+        if (!error && !uptodate)
+                error = -EIO;
+
+        if (error) {
+                /* doh. what now?
+                 * for now, set all bits, and flag MD_IO_ERROR */
+                __set_bit(BM_MD_IO_ERROR, &b->bm_flags);
+        }
+        if (atomic_dec_and_test(&b->bm_async_io))
+                wake_up(&b->bm_io_wait);
+
+        bio_put(bio);
+}
+
+static void bm_page_io_async(struct drbd_conf *mdev, struct drbd_bitmap *b, int page_nr, int rw) __must_hold(local)
+{
+        /* we are process context. we always get a bio */
+        struct bio *bio = bio_alloc(GFP_KERNEL, 1);
+        unsigned int len;
+        sector_t on_disk_sector =
+                mdev->ldev->md.md_offset + mdev->ldev->md.bm_offset;
+        on_disk_sector += ((sector_t)page_nr) << (PAGE_SHIFT-9);
+
+        /* this might happen with very small
+         * flexible external meta data device */
+        len = min_t(unsigned int, PAGE_SIZE,
+                (drbd_md_last_sector(mdev->ldev) - on_disk_sector + 1)<<9);
+
+        bio->bi_bdev = mdev->ldev->md_bdev;
+        bio->bi_sector = on_disk_sector;
+        bio_add_page(bio, b->bm_pages[page_nr], len, 0);
+        bio->bi_private = b;
+        bio->bi_end_io = bm_async_io_complete;
+
+        if (FAULT_ACTIVE(mdev, (rw & WRITE) ? DRBD_FAULT_MD_WR : DRBD_FAULT_MD_RD)) {
+                bio->bi_rw |= rw;
+                bio_endio(bio, -EIO);
+        } else {
+                submit_bio(rw, bio);
+        }
+}
+
+# if defined(__LITTLE_ENDIAN)
+        /* nothing to do, on disk == in memory */
+# define bm_cpu_to_lel(x) ((void)0)
+# else
+void bm_cpu_to_lel(struct drbd_bitmap *b)
+{
+        /* need to cpu_to_lel all the pages ...
+         * this may be optimized by using
+         * cpu_to_lel(-1) == -1 and cpu_to_lel(0) == 0;
+         * the following is still not optimal, but better than nothing */
+        unsigned int i;
+        unsigned long *p_addr, *bm;
+        if (b->bm_set == 0) {
+                /* no page at all; avoid swap if all is 0 */
+                i = b->bm_number_of_pages;
+        } else if (b->bm_set == b->bm_bits) {
+                /* only the last page */
+                i = b->bm_number_of_pages - 1;
+        } else {
+                /* all pages */
+                i = 0;
+        }
+        for (; i < b->bm_number_of_pages; i++) {
+                p_addr = kmap_atomic(b->bm_pages[i], KM_USER0);
+                for (bm = p_addr; bm < p_addr + PAGE_SIZE/sizeof(long); bm++)
+                        *bm = cpu_to_lel(*bm);
+                kunmap_atomic(p_addr, KM_USER0);
+        }
+}
+# endif
+/* lel_to_cpu == cpu_to_lel */
+# define bm_lel_to_cpu(x) bm_cpu_to_lel(x)
+
+/*
+ * bm_rw: read/write the whole bitmap from/to its on disk location.
+ */
+static int bm_rw(struct drbd_conf *mdev, int rw) __must_hold(local)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        /* sector_t sector; */
+        int bm_words, num_pages, i;
+        unsigned long now;
+        char ppb[10];
+        int err = 0;
+
+        WARN_ON(!bm_is_locked(b));
+
+        /* no spinlock here, the drbd_bm_lock should be enough! */
+
+        bm_words  = drbd_bm_words(mdev);
+        num_pages = (bm_words*sizeof(long) + PAGE_SIZE-1) >> PAGE_SHIFT;
+
+        /* on disk bitmap is little endian */
+        if (rw == WRITE)
+                bm_cpu_to_lel(b);
+
+        now = jiffies;
+        atomic_set(&b->bm_async_io, num_pages);
+        __clear_bit(BM_MD_IO_ERROR, &b->bm_flags);
+
+        /* let the layers below us try to merge these bios... */
+        for (i = 0; i < num_pages; i++)
+                bm_page_io_async(mdev, b, i, rw);
+
+        drbd_blk_run_queue(bdev_get_queue(mdev->ldev->md_bdev));
+        wait_event(b->bm_io_wait, atomic_read(&b->bm_async_io) == 0);
+
+        if (test_bit(BM_MD_IO_ERROR, &b->bm_flags)) {
+                dev_alert(DEV, "we had at least one MD IO ERROR during bitmap IO\n");
+                drbd_chk_io_error(mdev, 1, TRUE);
+                err = -EIO;
+        }
+
+        now = jiffies;
+        if (rw == WRITE) {
+                /* swap back endianness */
+                bm_lel_to_cpu(b);
+                /* flush bitmap to stable storage */
+                drbd_md_flush(mdev);
+        } else /* rw == READ */ {
+                /* just read, if necessary adjust endianness */
+                b->bm_set = bm_count_bits_swap_endian(b);
+                dev_info(DEV, "recounting of set bits took additional %lu jiffies\n",
+                     jiffies - now);
+        }
+        now = b->bm_set;
+
+        dev_info(DEV, "%s (%lu bits) marked out-of-sync by on disk bit-map.\n",
+             ppsize(ppb, now << (BM_BLOCK_SHIFT-10)), now);
+
+        return err;
+}
+
+/**
+ * drbd_bm_read() - Read the whole bitmap from its on disk location.
+ * @mdev:       DRBD device.
+ */
+int drbd_bm_read(struct drbd_conf *mdev) __must_hold(local)
+{
+        return bm_rw(mdev, READ);
+}
+
+/**
+ * drbd_bm_write() - Write the whole bitmap to its on disk location.
+ * @mdev:       DRBD device.
+ */
+int drbd_bm_write(struct drbd_conf *mdev) __must_hold(local)
+{
+        return bm_rw(mdev, WRITE);
+}
+
+/**
+ * drbd_bm_write_sect: Writes a 512 (MD_SECTOR_SIZE) byte piece of the bitmap
+ * @mdev:       DRBD device.
+ * @enr:        Extent number in the resync lru (happens to be sector offset)
+ *
+ * The BM_EXT_SIZE is on purpose exactly the amount of the bitmap covered
+ * by a single sector write. Therefore enr == sector offset from the
+ * start of the bitmap.
+ */
+int drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local)
+{
+        sector_t on_disk_sector = enr + mdev->ldev->md.md_offset
+                                      + mdev->ldev->md.bm_offset;
+        int bm_words, num_words, offset;
+        int err = 0;
+
+        mutex_lock(&mdev->md_io_mutex);
+        bm_words  = drbd_bm_words(mdev);
+        offset    = S2W(enr);   /* word offset into bitmap */
+        num_words = min(S2W(1), bm_words - offset);
+        if (num_words < S2W(1))
+                memset(page_address(mdev->md_io_page), 0, MD_SECTOR_SIZE);
+        drbd_bm_get_lel(mdev, offset, num_words,
+                        page_address(mdev->md_io_page));
+        if (!drbd_md_sync_page_io(mdev, mdev->ldev, on_disk_sector, WRITE)) {
+                int i;
+                err = -EIO;
+                dev_err(DEV, "IO ERROR writing bitmap sector %lu "
+                    "(meta-disk sector %llus)\n",
+                    enr, (unsigned long long)on_disk_sector);
+                drbd_chk_io_error(mdev, 1, TRUE);
+                for (i = 0; i < AL_EXT_PER_BM_SECT; i++)
+                        drbd_bm_ALe_set_all(mdev, enr*AL_EXT_PER_BM_SECT+i);
+        }
+        mdev->bm_writ_cnt++;
+        mutex_unlock(&mdev->md_io_mutex);
+        return err;
+}
+
+/* NOTE
+ * find_first_bit returns int, we return unsigned long.
+ * should not make much difference anyways, but ...
+ *
+ * this returns a bit number, NOT a sector!
+ */
+#define BPP_MASK ((1UL << (PAGE_SHIFT+3)) - 1)
+static unsigned long __bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo,
+        const int find_zero_bit, const enum km_type km)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long i = -1UL;
+        unsigned long *p_addr;
+        unsigned long bit_offset; /* bit offset of the mapped page. */
+
+        if (bm_fo > b->bm_bits) {
+                dev_err(DEV, "bm_fo=%lu bm_bits=%lu\n", bm_fo, b->bm_bits);
+        } else {
+                while (bm_fo < b->bm_bits) {
+                        unsigned long offset;
+                        bit_offset = bm_fo & ~BPP_MASK; /* bit offset of the page */
+                        offset = bit_offset >> LN2_BPL;    /* word offset of the page */
+                        p_addr = __bm_map_paddr(b, offset, km);
+
+                        if (find_zero_bit)
+                                i = find_next_zero_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+                        else
+                                i = find_next_bit(p_addr, PAGE_SIZE*8, bm_fo & BPP_MASK);
+
+                        __bm_unmap(p_addr, km);
+                        if (i < PAGE_SIZE*8) {
+                                i = bit_offset + i;
+                                if (i >= b->bm_bits)
+                                        break;
+                                goto found;
+                        }
+                        bm_fo = bit_offset + PAGE_SIZE*8;
+                }
+                i = -1UL;
+        }
+ found:
+        return i;
+}
+
+static unsigned long bm_find_next(struct drbd_conf *mdev,
+        unsigned long bm_fo, const int find_zero_bit)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long i = -1UL;
+
+        ERR_IF(!b) return i;
+        ERR_IF(!b->bm_pages) return i;
+
+        spin_lock_irq(&b->bm_lock);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        i = __bm_find_next(mdev, bm_fo, find_zero_bit, KM_IRQ1);
+
+        spin_unlock_irq(&b->bm_lock);
+        return i;
+}
+
+unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        return bm_find_next(mdev, bm_fo, 0);
+}
+
+#if 0
+/* not yet needed for anything. */
+unsigned long drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        return bm_find_next(mdev, bm_fo, 1);
+}
+#endif
+
+/* does not spin_lock_irqsave.
+ * you must take drbd_bm_lock() first */
+unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        /* WARN_ON(!bm_is_locked(mdev)); */
+        return __bm_find_next(mdev, bm_fo, 0, KM_USER1);
+}
+
+unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo)
+{
+        /* WARN_ON(!bm_is_locked(mdev)); */
+        return __bm_find_next(mdev, bm_fo, 1, KM_USER1);
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector.
+ * expected to be called for only a few bits (e - s about BITS_PER_LONG).
+ * Must hold bitmap lock already. */
+int __bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+        unsigned long e, int val, const enum km_type km)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr = NULL;
+        unsigned long bitnr;
+        unsigned long last_page_nr = -1UL;
+        int c = 0;
+
+        if (e >= b->bm_bits) {
+                dev_err(DEV, "ASSERT FAILED: bit_s=%lu bit_e=%lu bm_bits=%lu\n",
+                                s, e, b->bm_bits);
+                e = b->bm_bits ? b->bm_bits -1 : 0;
+        }
+        for (bitnr = s; bitnr <= e; bitnr++) {
+                unsigned long offset = bitnr>>LN2_BPL;
+                unsigned long page_nr = offset >> (PAGE_SHIFT - LN2_BPL + 3);
+                if (page_nr != last_page_nr) {
+                        if (p_addr)
+                                __bm_unmap(p_addr, km);
+                        p_addr = __bm_map_paddr(b, offset, km);
+                        last_page_nr = page_nr;
+                }
+                if (val)
+                        c += (0 == __test_and_set_bit(bitnr & BPP_MASK, p_addr));
+                else
+                        c -= (0 != __test_and_clear_bit(bitnr & BPP_MASK, p_addr));
+        }
+        if (p_addr)
+                __bm_unmap(p_addr, km);
+        b->bm_set += c;
+        return c;
+}
+
+/* returns number of bits actually changed.
+ * for val != 0, we change 0 -> 1, return code positive
+ * for val == 0, we change 1 -> 0, return code negative
+ * wants bitnr, not sector */
+int bm_change_bits_to(struct drbd_conf *mdev, const unsigned long s,
+        const unsigned long e, int val)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        int c = 0;
+
+        ERR_IF(!b) return 1;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        c = __bm_change_bits_to(mdev, s, e, val, KM_IRQ1);
+
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return c;
+}
+
+/* returns number of bits changed 0 -> 1 */
+int drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        return bm_change_bits_to(mdev, s, e, 1);
+}
+
+/* returns number of bits changed 1 -> 0 */
+int drbd_bm_clear_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        return -bm_change_bits_to(mdev, s, e, 0);
+}
+
+/* sets all bits in full words,
+ * from first_word up to, but not including, last_word */
+static inline void bm_set_full_words_within_one_page(struct drbd_bitmap *b,
+                int page_nr, int first_word, int last_word)
+{
+        int i;
+        int bits;
+        unsigned long *paddr = kmap_atomic(b->bm_pages[page_nr], KM_USER0);
+        for (i = first_word; i < last_word; i++) {
+                bits = hweight_long(paddr[i]);
+                paddr[i] = ~0UL;
+                b->bm_set += BITS_PER_LONG - bits;
+        }
+        kunmap_atomic(paddr, KM_USER0);
+}
+
+/* Same thing as drbd_bm_set_bits, but without taking the spin_lock_irqsave.
+ * You must first drbd_bm_lock().
+ * Can be called to set the whole bitmap in one go.
+ * Sets bits from s to e _inclusive_. */
+void _drbd_bm_set_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        /* First set_bit from the first bit (s)
+         * up to the next long boundary (sl),
+         * then assign full words up to the last long boundary (el),
+         * then set_bit up to and including the last bit (e).
+         *
+         * Do not use memset, because we must account for changes,
+         * so we need to loop over the words with hweight() anyways.
+         */
+        unsigned long sl = ALIGN(s,BITS_PER_LONG);
+        unsigned long el = (e+1) & ~((unsigned long)BITS_PER_LONG-1);
+        int first_page;
+        int last_page;
+        int page_nr;
+        int first_word;
+        int last_word;
+
+        if (e - s <= 3*BITS_PER_LONG) {
+                /* don't bother; el and sl may even be wrong. */
+                __bm_change_bits_to(mdev, s, e, 1, KM_USER0);
+                return;
+        }
+
+        /* difference is large enough that we can trust sl and el */
+
+        /* bits filling the current long */
+        if (sl)
+                __bm_change_bits_to(mdev, s, sl-1, 1, KM_USER0);
+
+        first_page = sl >> (3 + PAGE_SHIFT);
+        last_page = el >> (3 + PAGE_SHIFT);
+
+        /* MLPP: modulo longs per page */
+        /* LWPP: long words per page */
+        first_word = MLPP(sl >> LN2_BPL);
+        last_word = LWPP;
+
+        /* first and full pages, unless first page == last page */
+        for (page_nr = first_page; page_nr < last_page; page_nr++) {
+                bm_set_full_words_within_one_page(mdev->bitmap, page_nr, first_word, last_word);
+                cond_resched();
+                first_word = 0;
+        }
+
+        /* last page (respectively only page, for first page == last page) */
+        last_word = MLPP(el >> LN2_BPL);
+        bm_set_full_words_within_one_page(mdev->bitmap, last_page, first_word, last_word);
+
+        /* possibly trailing bits.
+         * example: (e & 63) == 63, el will be e+1.
+         * if that even was the very last bit,
+         * it would trigger an assert in __bm_change_bits_to()
+         */
+        if (el <= e)
+                __bm_change_bits_to(mdev, el, e, 1, KM_USER0);
+}
+
+/* returns bit state
+ * wants bitnr, NOT sector.
+ * inherently racy... area needs to be locked by means of {al,rs}_lru
+ *  1 ... bit set
+ *  0 ... bit not set
+ * -1 ... first out of bounds access, stop testing for bits!
+ */
+int drbd_bm_test_bit(struct drbd_conf *mdev, const unsigned long bitnr)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr;
+        int i;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        if (bitnr < b->bm_bits) {
+                unsigned long offset = bitnr>>LN2_BPL;
+                p_addr = bm_map_paddr(b, offset);
+                i = test_bit(bitnr & BPP_MASK, p_addr) ? 1 : 0;
+                bm_unmap(p_addr);
+        } else if (bitnr == b->bm_bits) {
+                i = -1;
+        } else { /* (bitnr > b->bm_bits) */
+                dev_err(DEV, "bitnr=%lu > bm_bits=%lu\n", bitnr, b->bm_bits);
+                i = 0;
+        }
+
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return i;
+}
+
+/* returns number of bits set in the range [s, e] */
+int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e)
+{
+        unsigned long flags;
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr = NULL, page_nr = -1;
+        unsigned long bitnr;
+        int c = 0;
+        size_t w;
+
+        /* If this is called without a bitmap, that is a bug.  But just to be
+         * robust in case we screwed up elsewhere, in that case pretend there
+         * was one dirty bit in the requested area, so we won't try to do a
+         * local read there (no bitmap probably implies no disk) */
+        ERR_IF(!b) return 1;
+        ERR_IF(!b->bm_pages) return 1;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        for (bitnr = s; bitnr <= e; bitnr++) {
+                w = bitnr >> LN2_BPL;
+                if (page_nr != w >> (PAGE_SHIFT - LN2_BPL + 3)) {
+                        page_nr = w >> (PAGE_SHIFT - LN2_BPL + 3);
+                        if (p_addr)
+                                bm_unmap(p_addr);
+                        p_addr = bm_map_paddr(b, w);
+                }
+                ERR_IF (bitnr >= b->bm_bits) {
+                        dev_err(DEV, "bitnr=%lu bm_bits=%lu\n", bitnr, b->bm_bits);
+                } else {
+                        c += (0 != test_bit(bitnr - (page_nr << (PAGE_SHIFT+3)), p_addr));
+                }
+        }
+        if (p_addr)
+                bm_unmap(p_addr);
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return c;
+}
+
+
+/* inherently racy...
+ * return value may be already out-of-date when this function returns.
+ * but the general usage is that this is only use during a cstate when bits are
+ * only cleared, not set, and typically only care for the case when the return
+ * value is zero, or we already "locked" this "bitmap extent" by other means.
+ *
+ * enr is bm-extent number, since we chose to name one sector (512 bytes)
+ * worth of the bitmap a "bitmap extent".
+ *
+ * TODO
+ * I think since we use it like a reference count, we should use the real
+ * reference count of some bitmap extent element from some lru instead...
+ *
+ */
+int drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        int count, s, e;
+        unsigned long flags;
+        unsigned long *p_addr, *bm;
+
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irqsave(&b->bm_lock, flags);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+
+        s = S2W(enr);
+        e = min((size_t)S2W(enr+1), b->bm_words);
+        count = 0;
+        if (s < b->bm_words) {
+                int n = e-s;
+                p_addr = bm_map_paddr(b, s);
+                bm = p_addr + MLPP(s);
+                while (n--)
+                        count += hweight_long(*bm++);
+                bm_unmap(p_addr);
+        } else {
+                dev_err(DEV, "start offset (%d) too large in drbd_bm_e_weight\n", s);
+        }
+        spin_unlock_irqrestore(&b->bm_lock, flags);
+        return count;
+}
+
+/* set all bits covered by the AL-extent al_enr */
+unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev, unsigned long al_enr)
+{
+        struct drbd_bitmap *b = mdev->bitmap;
+        unsigned long *p_addr, *bm;
+        unsigned long weight;
+        int count, s, e, i, do_now;
+        ERR_IF(!b) return 0;
+        ERR_IF(!b->bm_pages) return 0;
+
+        spin_lock_irq(&b->bm_lock);
+        if (bm_is_locked(b))
+                bm_print_lock_info(mdev);
+        weight = b->bm_set;
+
+        s = al_enr * BM_WORDS_PER_AL_EXT;
+        e = min_t(size_t, s + BM_WORDS_PER_AL_EXT, b->bm_words);
+        /* assert that s and e are on the same page */
+        D_ASSERT((e-1) >> (PAGE_SHIFT - LN2_BPL + 3)
+              ==  s    >> (PAGE_SHIFT - LN2_BPL + 3));
+        count = 0;
+        if (s < b->bm_words) {
+                i = do_now = e-s;
+                p_addr = bm_map_paddr(b, s);
+                bm = p_addr + MLPP(s);
+                while (i--) {
+                        count += hweight_long(*bm);
+                        *bm = -1UL;
+                        bm++;
+                }
+                bm_unmap(p_addr);
+                b->bm_set += do_now*BITS_PER_LONG - count;
+                if (e == b->bm_words)
+                        b->bm_set -= bm_clear_surplus(b);
+        } else {
+                dev_err(DEV, "start offset (%d) too large in drbd_bm_ALe_set_all\n", s);
+        }
+        weight = b->bm_set - weight;
+        spin_unlock_irq(&b->bm_lock);
+        return weight;
+}
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
new file mode 100644
index 000000000000..8da602e010bb
--- /dev/null
+++ b/drivers/block/drbd/drbd_int.h
@@ -0,0 +1,2258 @@
+/*
+  drbd_int.h
+
+  This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+  Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+  Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+  Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+  drbd is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2, or (at your option)
+  any later version.
+
+  drbd is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with drbd; see the file COPYING.  If not, write to
+  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#ifndef _DRBD_INT_H
+#define _DRBD_INT_H
+
+#include <linux/compiler.h>
+#include <linux/types.h>
+#include <linux/version.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/crypto.h>
+#include <linux/tcp.h>
+#include <linux/mutex.h>
+#include <linux/major.h>
+#include <linux/blkdev.h>
+#include <linux/genhd.h>
+#include <net/tcp.h>
+#include <linux/lru_cache.h>
+
+#ifdef __CHECKER__
+# define __protected_by(x)       __attribute__((require_context(x,1,999,"rdwr")))
+# define __protected_read_by(x)  __attribute__((require_context(x,1,999,"read")))
+# define __protected_write_by(x) __attribute__((require_context(x,1,999,"write")))
+# define __must_hold(x)       __attribute__((context(x,1,1), require_context(x,1,999,"call")))
+#else
+# define __protected_by(x)
+# define __protected_read_by(x)
+# define __protected_write_by(x)
+# define __must_hold(x)
+#endif
+
+#define __no_warn(lock, stmt) do { __acquire(lock); stmt; __release(lock); } while (0)
+
+/* module parameter, defined in drbd_main.c */
+extern unsigned int minor_count;
+extern int disable_sendpage;
+extern int allow_oos;
+extern unsigned int cn_idx;
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+extern int enable_faults;
+extern int fault_rate;
+extern int fault_devs;
+#endif
+
+extern char usermode_helper[];
+
+
+#ifndef TRUE
+#define TRUE 1
+#endif
+#ifndef FALSE
+#define FALSE 0
+#endif
+
+/* I don't remember why XCPU ...
+ * This is used to wake the asender,
+ * and to interrupt sending the sending task
+ * on disconnect.
+ */
+#define DRBD_SIG SIGXCPU
+
+/* This is used to stop/restart our threads.
+ * Cannot use SIGTERM nor SIGKILL, since these
+ * are sent out by init on runlevel changes
+ * I choose SIGHUP for now.
+ */
+#define DRBD_SIGKILL SIGHUP
+
+/* All EEs on the free list should have ID_VACANT (== 0)
+ * freshly allocated EEs get !ID_VACANT (== 1)
+ * so if it says "cannot dereference null pointer at adress 0x00000001",
+ * it is most likely one of these :( */
+
+#define ID_IN_SYNC      (4711ULL)
+#define ID_OUT_OF_SYNC  (4712ULL)
+
+#define ID_SYNCER (-1ULL)
+#define ID_VACANT 0
+#define is_syncer_block_id(id) ((id) == ID_SYNCER)
+
+struct drbd_conf;
+
+
+/* to shorten dev_warn(DEV, "msg"); and relatives statements */
+#define DEV (disk_to_dev(mdev->vdisk))
+
+#define D_ASSERT(exp)   if (!(exp)) \
+         dev_err(DEV, "ASSERT( " #exp " ) in %s:%d\n", __FILE__, __LINE__)
+
+#define ERR_IF(exp) if (({                              \
+        int _b = (exp) != 0;                            \
+        if (_b) dev_err(DEV, "%s: (%s) in %s:%d\n",     \
+                __func__, #exp, __FILE__, __LINE__);    \
+         _b;                                            \
+        }))
+
+/* Defines to control fault insertion */
+enum {
+        DRBD_FAULT_MD_WR = 0,   /* meta data write */
+        DRBD_FAULT_MD_RD = 1,   /*           read  */
+        DRBD_FAULT_RS_WR = 2,   /* resync          */
+        DRBD_FAULT_RS_RD = 3,
+        DRBD_FAULT_DT_WR = 4,   /* data            */
+        DRBD_FAULT_DT_RD = 5,
+        DRBD_FAULT_DT_RA = 6,   /* data read ahead */
+        DRBD_FAULT_BM_ALLOC = 7,        /* bitmap allocation */
+        DRBD_FAULT_AL_EE = 8,   /* alloc ee */
+
+        DRBD_FAULT_MAX,
+};
+
+extern void trace_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, ...);
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+extern unsigned int
+_drbd_insert_fault(struct drbd_conf *mdev, unsigned int type);
+static inline int
+drbd_insert_fault(struct drbd_conf *mdev, unsigned int type) {
+        return fault_rate &&
+                (enable_faults & (1<<type)) &&
+                _drbd_insert_fault(mdev, type);
+}
+#define FAULT_ACTIVE(_m, _t) (drbd_insert_fault((_m), (_t)))
+
+#else
+#define FAULT_ACTIVE(_m, _t) (0)
+#endif
+
+/* integer division, round _UP_ to the next integer */
+#define div_ceil(A, B) ((A)/(B) + ((A)%(B) ? 1 : 0))
+/* usual integer division */
+#define div_floor(A, B) ((A)/(B))
+
+/* drbd_meta-data.c (still in drbd_main.c) */
+/* 4th incarnation of the disk layout. */
+#define DRBD_MD_MAGIC (DRBD_MAGIC+4)
+
+extern struct drbd_conf **minor_table;
+extern struct ratelimit_state drbd_ratelimit_state;
+
+/* on the wire */
+enum drbd_packets {
+        /* receiver (data socket) */
+        P_DATA                = 0x00,
+        P_DATA_REPLY          = 0x01, /* Response to P_DATA_REQUEST */
+        P_RS_DATA_REPLY       = 0x02, /* Response to P_RS_DATA_REQUEST */
+        P_BARRIER             = 0x03,
+        P_BITMAP              = 0x04,
+        P_BECOME_SYNC_TARGET  = 0x05,
+        P_BECOME_SYNC_SOURCE  = 0x06,
+        P_UNPLUG_REMOTE       = 0x07, /* Used at various times to hint the peer */
+        P_DATA_REQUEST        = 0x08, /* Used to ask for a data block */
+        P_RS_DATA_REQUEST     = 0x09, /* Used to ask for a data block for resync */
+        P_SYNC_PARAM          = 0x0a,
+        P_PROTOCOL            = 0x0b,
+        P_UUIDS               = 0x0c,
+        P_SIZES               = 0x0d,
+        P_STATE               = 0x0e,
+        P_SYNC_UUID           = 0x0f,
+        P_AUTH_CHALLENGE      = 0x10,
+        P_AUTH_RESPONSE       = 0x11,
+        P_STATE_CHG_REQ       = 0x12,
+
+        /* asender (meta socket */
+        P_PING                = 0x13,
+        P_PING_ACK            = 0x14,
+        P_RECV_ACK            = 0x15, /* Used in protocol B */
+        P_WRITE_ACK           = 0x16, /* Used in protocol C */
+        P_RS_WRITE_ACK        = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
+        P_DISCARD_ACK         = 0x18, /* Used in proto C, two-primaries conflict detection */
+        P_NEG_ACK             = 0x19, /* Sent if local disk is unusable */
+        P_NEG_DREPLY          = 0x1a, /* Local disk is broken... */
+        P_NEG_RS_DREPLY       = 0x1b, /* Local disk is broken... */
+        P_BARRIER_ACK         = 0x1c,
+        P_STATE_CHG_REPLY     = 0x1d,
+
+        /* "new" commands, no longer fitting into the ordering scheme above */
+
+        P_OV_REQUEST          = 0x1e, /* data socket */
+        P_OV_REPLY            = 0x1f,
+        P_OV_RESULT           = 0x20, /* meta socket */
+        P_CSUM_RS_REQUEST     = 0x21, /* data socket */
+        P_RS_IS_IN_SYNC       = 0x22, /* meta socket */
+        P_SYNC_PARAM89        = 0x23, /* data socket, protocol version 89 replacement for P_SYNC_PARAM */
+        P_COMPRESSED_BITMAP   = 0x24, /* compressed or otherwise encoded bitmap transfer */
+
+        P_MAX_CMD             = 0x25,
+        P_MAY_IGNORE          = 0x100, /* Flag to test if (cmd > P_MAY_IGNORE) ... */
+        P_MAX_OPT_CMD         = 0x101,
+
+        /* special command ids for handshake */
+
+        P_HAND_SHAKE_M        = 0xfff1, /* First Packet on the MetaSock */
+        P_HAND_SHAKE_S        = 0xfff2, /* First Packet on the Socket */
+
+        P_HAND_SHAKE          = 0xfffe  /* FIXED for the next century! */
+};
+
+static inline const char *cmdname(enum drbd_packets cmd)
+{
+        /* THINK may need to become several global tables
+         * when we want to support more than
+         * one PRO_VERSION */
+        static const char *cmdnames[] = {
+                [P_DATA]                = "Data",
+                [P_DATA_REPLY]          = "DataReply",
+                [P_RS_DATA_REPLY]       = "RSDataReply",
+                [P_BARRIER]             = "Barrier",
+                [P_BITMAP]              = "ReportBitMap",
+                [P_BECOME_SYNC_TARGET]  = "BecomeSyncTarget",
+                [P_BECOME_SYNC_SOURCE]  = "BecomeSyncSource",
+                [P_UNPLUG_REMOTE]       = "UnplugRemote",
+                [P_DATA_REQUEST]        = "DataRequest",
+                [P_RS_DATA_REQUEST]     = "RSDataRequest",
+                [P_SYNC_PARAM]          = "SyncParam",
+                [P_SYNC_PARAM89]        = "SyncParam89",
+                [P_PROTOCOL]            = "ReportProtocol",
+                [P_UUIDS]               = "ReportUUIDs",
+                [P_SIZES]               = "ReportSizes",
+                [P_STATE]               = "ReportState",
+                [P_SYNC_UUID]           = "ReportSyncUUID",
+                [P_AUTH_CHALLENGE]      = "AuthChallenge",
+                [P_AUTH_RESPONSE]       = "AuthResponse",
+                [P_PING]                = "Ping",
+                [P_PING_ACK]            = "PingAck",
+                [P_RECV_ACK]            = "RecvAck",
+                [P_WRITE_ACK]           = "WriteAck",
+                [P_RS_WRITE_ACK]        = "RSWriteAck",
+                [P_DISCARD_ACK]         = "DiscardAck",
+                [P_NEG_ACK]             = "NegAck",
+                [P_NEG_DREPLY]          = "NegDReply",
+                [P_NEG_RS_DREPLY]       = "NegRSDReply",
+                [P_BARRIER_ACK]         = "BarrierAck",
+                [P_STATE_CHG_REQ]       = "StateChgRequest",
+                [P_STATE_CHG_REPLY]     = "StateChgReply",
+                [P_OV_REQUEST]          = "OVRequest",
+                [P_OV_REPLY]            = "OVReply",
+                [P_OV_RESULT]           = "OVResult",
+                [P_MAX_CMD]             = NULL,
+        };
+
+        if (cmd == P_HAND_SHAKE_M)
+                return "HandShakeM";
+        if (cmd == P_HAND_SHAKE_S)
+                return "HandShakeS";
+        if (cmd == P_HAND_SHAKE)
+                return "HandShake";
+        if (cmd >= P_MAX_CMD)
+                return "Unknown";
+        return cmdnames[cmd];
+}
+
+/* for sending/receiving the bitmap,
+ * possibly in some encoding scheme */
+struct bm_xfer_ctx {
+        /* "const"
+         * stores total bits and long words
+         * of the bitmap, so we don't need to
+         * call the accessor functions over and again. */
+        unsigned long bm_bits;
+        unsigned long bm_words;
+        /* during xfer, current position within the bitmap */
+        unsigned long bit_offset;
+        unsigned long word_offset;
+
+        /* statistics; index: (h->command == P_BITMAP) */
+        unsigned packets[2];
+        unsigned bytes[2];
+};
+
+extern void INFO_bm_xfer_stats(struct drbd_conf *mdev,
+                const char *direction, struct bm_xfer_ctx *c);
+
+static inline void bm_xfer_ctx_bit_to_word_offset(struct bm_xfer_ctx *c)
+{
+        /* word_offset counts "native long words" (32 or 64 bit),
+         * aligned at 64 bit.
+         * Encoded packet may end at an unaligned bit offset.
+         * In case a fallback clear text packet is transmitted in
+         * between, we adjust this offset back to the last 64bit
+         * aligned "native long word", which makes coding and decoding
+         * the plain text bitmap much more convenient.  */
+#if BITS_PER_LONG == 64
+        c->word_offset = c->bit_offset >> 6;
+#elif BITS_PER_LONG == 32
+        c->word_offset = c->bit_offset >> 5;
+        c->word_offset &= ~(1UL);
+#else
+# error "unsupported BITS_PER_LONG"
+#endif
+}
+
+#ifndef __packed
+#define __packed __attribute__((packed))
+#endif
+
+/* This is the layout for a packet on the wire.
+ * The byteorder is the network byte order.
+ *     (except block_id and barrier fields.
+ *      these are pointers to local structs
+ *      and have no relevance for the partner,
+ *      which just echoes them as received.)
+ *
+ * NOTE that the payload starts at a long aligned offset,
+ * regardless of 32 or 64 bit arch!
+ */
+struct p_header {
+        u32       magic;
+        u16       command;
+        u16       length;       /* bytes of data after this header */
+        u8        payload[0];
+} __packed;
+/* 8 bytes. packet FIXED for the next century! */
+
+/*
+ * short commands, packets without payload, plain p_header:
+ *   P_PING
+ *   P_PING_ACK
+ *   P_BECOME_SYNC_TARGET
+ *   P_BECOME_SYNC_SOURCE
+ *   P_UNPLUG_REMOTE
+ */
+
+/*
+ * commands with out-of-struct payload:
+ *   P_BITMAP    (no additional fields)
+ *   P_DATA, P_DATA_REPLY (see p_data)
+ *   P_COMPRESSED_BITMAP (see receive_compressed_bitmap)
+ */
+
+/* these defines must not be changed without changing the protocol version */
+#define DP_HARDBARRIER        1
+#define DP_RW_SYNC            2
+#define DP_MAY_SET_IN_SYNC    4
+
+struct p_data {
+        struct p_header head;
+        u64         sector;    /* 64 bits sector number */
+        u64         block_id;  /* to identify the request in protocol B&C */
+        u32         seq_num;
+        u32         dp_flags;
+} __packed;
+
+/*
+ * commands which share a struct:
+ *  p_block_ack:
+ *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
+ *   P_DISCARD_ACK (proto C, two-primaries conflict detection)
+ *  p_block_req:
+ *   P_DATA_REQUEST, P_RS_DATA_REQUEST
+ */
+struct p_block_ack {
+        struct p_header head;
+        u64         sector;
+        u64         block_id;
+        u32         blksize;
+        u32         seq_num;
+} __packed;
+
+
+struct p_block_req {
+        struct p_header head;
+        u64 sector;
+        u64 block_id;
+        u32 blksize;
+        u32 pad;        /* to multiple of 8 Byte */
+} __packed;
+
+/*
+ * commands with their own struct for additional fields:
+ *   P_HAND_SHAKE
+ *   P_BARRIER
+ *   P_BARRIER_ACK
+ *   P_SYNC_PARAM
+ *   ReportParams
+ */
+
+struct p_handshake {
+        struct p_header head;   /* 8 bytes */
+        u32 protocol_min;
+        u32 feature_flags;
+        u32 protocol_max;
+
+        /* should be more than enough for future enhancements
+         * for now, feature_flags and the reserverd array shall be zero.
+         */
+
+        u32 _pad;
+        u64 reserverd[7];
+} __packed;
+/* 80 bytes, FIXED for the next century */
+
+struct p_barrier {
+        struct p_header head;
+        u32 barrier;    /* barrier number _handle_ only */
+        u32 pad;        /* to multiple of 8 Byte */
+} __packed;
+
+struct p_barrier_ack {
+        struct p_header head;
+        u32 barrier;
+        u32 set_size;
+} __packed;
+
+struct p_rs_param {
+        struct p_header head;
+        u32 rate;
+
+              /* Since protocol version 88 and higher. */
+        char verify_alg[0];
+} __packed;
+
+struct p_rs_param_89 {
+        struct p_header head;
+        u32 rate;
+        /* protocol version 89: */
+        char verify_alg[SHARED_SECRET_MAX];
+        char csums_alg[SHARED_SECRET_MAX];
+} __packed;
+
+struct p_protocol {
+        struct p_header head;
+        u32 protocol;
+        u32 after_sb_0p;
+        u32 after_sb_1p;
+        u32 after_sb_2p;
+        u32 want_lose;
+        u32 two_primaries;
+
+              /* Since protocol version 87 and higher. */
+        char integrity_alg[0];
+
+} __packed;
+
+struct p_uuids {
+        struct p_header head;
+        u64 uuid[UI_EXTENDED_SIZE];
+} __packed;
+
+struct p_rs_uuid {
+        struct p_header head;
+        u64         uuid;
+} __packed;
+
+struct p_sizes {
+        struct p_header head;
+        u64         d_size;  /* size of disk */
+        u64         u_size;  /* user requested size */
+        u64         c_size;  /* current exported size */
+        u32         max_segment_size;  /* Maximal size of a BIO */
+        u32         queue_order_type;
+} __packed;
+
+struct p_state {
+        struct p_header head;
+        u32         state;
+} __packed;
+
+struct p_req_state {
+        struct p_header head;
+        u32         mask;
+        u32         val;
+} __packed;
+
+struct p_req_state_reply {
+        struct p_header head;
+        u32         retcode;
+} __packed;
+
+struct p_drbd06_param {
+        u64       size;
+        u32       state;
+        u32       blksize;
+        u32       protocol;
+        u32       version;
+        u32       gen_cnt[5];
+        u32       bit_map_gen[5];
+} __packed;
+
+struct p_discard {
+        struct p_header head;
+        u64         block_id;
+        u32         seq_num;
+        u32         pad;
+} __packed;
+
+/* Valid values for the encoding field.
+ * Bump proto version when changing this. */
+enum drbd_bitmap_code {
+        /* RLE_VLI_Bytes = 0,
+         * and other bit variants had been defined during
+         * algorithm evaluation. */
+        RLE_VLI_Bits = 2,
+};
+
+struct p_compressed_bm {
+        struct p_header head;
+        /* (encoding & 0x0f): actual encoding, see enum drbd_bitmap_code
+         * (encoding & 0x80): polarity (set/unset) of first runlength
+         * ((encoding >> 4) & 0x07): pad_bits, number of trailing zero bits
+         * used to pad up to head.length bytes
+         */
+        u8 encoding;
+
+        u8 code[0];
+} __packed;
+
+/* DCBP: Drbd Compressed Bitmap Packet ... */
+static inline enum drbd_bitmap_code
+DCBP_get_code(struct p_compressed_bm *p)
+{
+        return (enum drbd_bitmap_code)(p->encoding & 0x0f);
+}
+
+static inline void
+DCBP_set_code(struct p_compressed_bm *p, enum drbd_bitmap_code code)
+{
+        BUG_ON(code & ~0xf);
+        p->encoding = (p->encoding & ~0xf) | code;
+}
+
+static inline int
+DCBP_get_start(struct p_compressed_bm *p)
+{
+        return (p->encoding & 0x80) != 0;
+}
+
+static inline void
+DCBP_set_start(struct p_compressed_bm *p, int set)
+{
+        p->encoding = (p->encoding & ~0x80) | (set ? 0x80 : 0);
+}
+
+static inline int
+DCBP_get_pad_bits(struct p_compressed_bm *p)
+{
+        return (p->encoding >> 4) & 0x7;
+}
+
+static inline void
+DCBP_set_pad_bits(struct p_compressed_bm *p, int n)
+{
+        BUG_ON(n & ~0x7);
+        p->encoding = (p->encoding & (~0x7 << 4)) | (n << 4);
+}
+
+/* one bitmap packet, including the p_header,
+ * should fit within one _architecture independend_ page.
+ * so we need to use the fixed size 4KiB page size
+ * most architechtures have used for a long time.
+ */
+#define BM_PACKET_PAYLOAD_BYTES (4096 - sizeof(struct p_header))
+#define BM_PACKET_WORDS (BM_PACKET_PAYLOAD_BYTES/sizeof(long))
+#define BM_PACKET_VLI_BYTES_MAX (4096 - sizeof(struct p_compressed_bm))
+#if (PAGE_SIZE < 4096)
+/* drbd_send_bitmap / receive_bitmap would break horribly */
+#error "PAGE_SIZE too small"
+#endif
+
+union p_polymorph {
+        struct p_header          header;
+        struct p_handshake       handshake;
+        struct p_data            data;
+        struct p_block_ack       block_ack;
+        struct p_barrier         barrier;
+        struct p_barrier_ack     barrier_ack;
+        struct p_rs_param_89     rs_param_89;
+        struct p_protocol        protocol;
+        struct p_sizes           sizes;
+        struct p_uuids           uuids;
+        struct p_state           state;
+        struct p_req_state       req_state;
+        struct p_req_state_reply req_state_reply;
+        struct p_block_req       block_req;
+} __packed;
+
+/**********************************************************************/
+enum drbd_thread_state {
+        None,
+        Running,
+        Exiting,
+        Restarting
+};
+
+struct drbd_thread {
+        spinlock_t t_lock;
+        struct task_struct *task;
+        struct completion stop;
+        enum drbd_thread_state t_state;
+        int (*function) (struct drbd_thread *);
+        struct drbd_conf *mdev;
+        int reset_cpu_mask;
+};
+
+static inline enum drbd_thread_state get_t_state(struct drbd_thread *thi)
+{
+        /* THINK testing the t_state seems to be uncritical in all cases
+         * (but thread_{start,stop}), so we can read it *without* the lock.
+         *      --lge */
+
+        smp_rmb();
+        return thi->t_state;
+}
+
+
+/*
+ * Having this as the first member of a struct provides sort of "inheritance".
+ * "derived" structs can be "drbd_queue_work()"ed.
+ * The callback should know and cast back to the descendant struct.
+ * drbd_request and drbd_epoch_entry are descendants of drbd_work.
+ */
+struct drbd_work;
+typedef int (*drbd_work_cb)(struct drbd_conf *, struct drbd_work *, int cancel);
+struct drbd_work {
+        struct list_head list;
+        drbd_work_cb cb;
+};
+
+struct drbd_tl_epoch;
+struct drbd_request {
+        struct drbd_work w;
+        struct drbd_conf *mdev;
+
+        /* if local IO is not allowed, will be NULL.
+         * if local IO _is_ allowed, holds the locally submitted bio clone,
+         * or, after local IO completion, the ERR_PTR(error).
+         * see drbd_endio_pri(). */
+        struct bio *private_bio;
+
+        struct hlist_node colision;
+        sector_t sector;
+        unsigned int size;
+        unsigned int epoch; /* barrier_nr */
+
+        /* barrier_nr: used to check on "completion" whether this req was in
+         * the current epoch, and we therefore have to close it,
+         * starting a new epoch...
+         */
+
+        /* up to here, the struct layout is identical to drbd_epoch_entry;
+         * we might be able to use that to our advantage...  */
+
+        struct list_head tl_requests; /* ring list in the transfer log */
+        struct bio *master_bio;       /* master bio pointer */
+        unsigned long rq_state; /* see comments above _req_mod() */
+        int seq_num;
+        unsigned long start_time;
+};
+
+struct drbd_tl_epoch {
+        struct drbd_work w;
+        struct list_head requests; /* requests before */
+        struct drbd_tl_epoch *next; /* pointer to the next barrier */
+        unsigned int br_number;  /* the barriers identifier. */
+        int n_req;      /* number of requests attached before this barrier */
+};
+
+struct drbd_request;
+
+/* These Tl_epoch_entries may be in one of 6 lists:
+   active_ee .. data packet being written
+   sync_ee   .. syncer block being written
+   done_ee   .. block written, need to send P_WRITE_ACK
+   read_ee   .. [RS]P_DATA_REQUEST being read
+*/
+
+struct drbd_epoch {
+        struct list_head list;
+        unsigned int barrier_nr;
+        atomic_t epoch_size; /* increased on every request added. */
+        atomic_t active;     /* increased on every req. added, and dec on every finished. */
+        unsigned long flags;
+};
+
+/* drbd_epoch flag bits */
+enum {
+        DE_BARRIER_IN_NEXT_EPOCH_ISSUED,
+        DE_BARRIER_IN_NEXT_EPOCH_DONE,
+        DE_CONTAINS_A_BARRIER,
+        DE_HAVE_BARRIER_NUMBER,
+        DE_IS_FINISHING,
+};
+
+enum epoch_event {
+        EV_PUT,
+        EV_GOT_BARRIER_NR,
+        EV_BARRIER_DONE,
+        EV_BECAME_LAST,
+        EV_TRACE_FLUSH,       /* TRACE_ are not real events, only used for tracing */
+        EV_TRACE_ADD_BARRIER, /* Doing the first write as a barrier write */
+        EV_TRACE_SETTING_BI,  /* Barrier is expressed with the first write of the next epoch */
+        EV_TRACE_ALLOC,
+        EV_TRACE_FREE,
+        EV_CLEANUP = 32, /* used as flag */
+};
+
+struct drbd_epoch_entry {
+        struct drbd_work    w;
+        struct drbd_conf *mdev;
+        struct bio *private_bio;
+        struct hlist_node colision;
+        sector_t sector;
+        unsigned int size;
+        struct drbd_epoch *epoch;
+
+        /* up to here, the struct layout is identical to drbd_request;
+         * we might be able to use that to our advantage...  */
+
+        unsigned int flags;
+        u64    block_id;
+};
+
+struct drbd_wq_barrier {
+        struct drbd_work w;
+        struct completion done;
+};
+
+struct digest_info {
+        int digest_size;
+        void *digest;
+};
+
+/* ee flag bits */
+enum {
+        __EE_CALL_AL_COMPLETE_IO,
+        __EE_CONFLICT_PENDING,
+        __EE_MAY_SET_IN_SYNC,
+        __EE_IS_BARRIER,
+};
+#define EE_CALL_AL_COMPLETE_IO (1<<__EE_CALL_AL_COMPLETE_IO)
+#define EE_CONFLICT_PENDING    (1<<__EE_CONFLICT_PENDING)
+#define EE_MAY_SET_IN_SYNC     (1<<__EE_MAY_SET_IN_SYNC)
+#define EE_IS_BARRIER          (1<<__EE_IS_BARRIER)
+
+/* global flag bits */
+enum {
+        CREATE_BARRIER,         /* next P_DATA is preceeded by a P_BARRIER */
+        SIGNAL_ASENDER,         /* whether asender wants to be interrupted */
+        SEND_PING,              /* whether asender should send a ping asap */
+
+        STOP_SYNC_TIMER,        /* tell timer to cancel itself */
+        UNPLUG_QUEUED,          /* only relevant with kernel 2.4 */
+        UNPLUG_REMOTE,          /* sending a "UnplugRemote" could help */
+        MD_DIRTY,               /* current uuids and flags not yet on disk */
+        DISCARD_CONCURRENT,     /* Set on one node, cleared on the peer! */
+        USE_DEGR_WFC_T,         /* degr-wfc-timeout instead of wfc-timeout. */
+        CLUSTER_ST_CHANGE,      /* Cluster wide state change going on... */
+        CL_ST_CHG_SUCCESS,
+        CL_ST_CHG_FAIL,
+        CRASHED_PRIMARY,        /* This node was a crashed primary.
+                                 * Gets cleared when the state.conn
+                                 * goes into C_CONNECTED state. */
+        WRITE_BM_AFTER_RESYNC,  /* A kmalloc() during resync failed */
+        NO_BARRIER_SUPP,        /* underlying block device doesn't implement barriers */
+        CONSIDER_RESYNC,
+
+        MD_NO_BARRIER,          /* meta data device does not support barriers,
+                                   so don't even try */
+        SUSPEND_IO,             /* suspend application io */
+        BITMAP_IO,              /* suspend application io;
+                                   once no more io in flight, start bitmap io */
+        BITMAP_IO_QUEUED,       /* Started bitmap IO */
+        RESYNC_AFTER_NEG,       /* Resync after online grow after the attach&negotiate finished. */
+        NET_CONGESTED,          /* The data socket is congested */
+
+        CONFIG_PENDING,         /* serialization of (re)configuration requests.
+                                 * if set, also prevents the device from dying */
+        DEVICE_DYING,           /* device became unconfigured,
+                                 * but worker thread is still handling the cleanup.
+                                 * reconfiguring (nl_disk_conf, nl_net_conf) is dissalowed,
+                                 * while this is set. */
+        RESIZE_PENDING,         /* Size change detected locally, waiting for the response from
+                                 * the peer, if it changed there as well. */
+};
+
+struct drbd_bitmap; /* opaque for drbd_conf */
+
+/* TODO sort members for performance
+ * MAYBE group them further */
+
+/* THINK maybe we actually want to use the default "event/%s" worker threads
+ * or similar in linux 2.6, which uses per cpu data and threads.
+ *
+ * To be general, this might need a spin_lock member.
+ * For now, please use the mdev->req_lock to protect list_head,
+ * see drbd_queue_work below.
+ */
+struct drbd_work_queue {
+        struct list_head q;
+        struct semaphore s; /* producers up it, worker down()s it */
+        spinlock_t q_lock;  /* to protect the list. */
+};
+
+struct drbd_socket {
+        struct drbd_work_queue work;
+        struct mutex mutex;
+        struct socket    *socket;
+        /* this way we get our
+         * send/receive buffers off the stack */
+        union p_polymorph sbuf;
+        union p_polymorph rbuf;
+};
+
+struct drbd_md {
+        u64 md_offset;          /* sector offset to 'super' block */
+
+        u64 la_size_sect;       /* last agreed size, unit sectors */
+        u64 uuid[UI_SIZE];
+        u64 device_uuid;
+        u32 flags;
+        u32 md_size_sect;
+
+        s32 al_offset;  /* signed relative sector offset to al area */
+        s32 bm_offset;  /* signed relative sector offset to bitmap */
+
+        /* u32 al_nr_extents;      important for restoring the AL
+         * is stored into  sync_conf.al_extents, which in turn
+         * gets applied to act_log->nr_elements
+         */
+};
+
+/* for sync_conf and other types... */
+#define NL_PACKET(name, number, fields) struct name { fields };
+#define NL_INTEGER(pn,pr,member) int member;
+#define NL_INT64(pn,pr,member) __u64 member;
+#define NL_BIT(pn,pr,member)   unsigned member:1;
+#define NL_STRING(pn,pr,member,len) unsigned char member[len]; int member ## _len;
+#include "linux/drbd_nl.h"
+
+struct drbd_backing_dev {
+        struct block_device *backing_bdev;
+        struct block_device *md_bdev;
+        struct file *lo_file;
+        struct file *md_file;
+        struct drbd_md md;
+        struct disk_conf dc; /* The user provided config... */
+        sector_t known_size; /* last known size of that backing device */
+};
+
+struct drbd_md_io {
+        struct drbd_conf *mdev;
+        struct completion event;
+        int error;
+};
+
+struct bm_io_work {
+        struct drbd_work w;
+        char *why;
+        int (*io_fn)(struct drbd_conf *mdev);
+        void (*done)(struct drbd_conf *mdev, int rv);
+};
+
+enum write_ordering_e {
+        WO_none,
+        WO_drain_io,
+        WO_bdev_flush,
+        WO_bio_barrier
+};
+
+struct drbd_conf {
+        /* things that are stored as / read from meta data on disk */
+        unsigned long flags;
+
+        /* configured by drbdsetup */
+        struct net_conf *net_conf; /* protected by get_net_conf() and put_net_conf() */
+        struct syncer_conf sync_conf;
+        struct drbd_backing_dev *ldev __protected_by(local);
+
+        sector_t p_size;     /* partner's disk size */
+        struct request_queue *rq_queue;
+        struct block_device *this_bdev;
+        struct gendisk      *vdisk;
+
+        struct drbd_socket data; /* data/barrier/cstate/parameter packets */
+        struct drbd_socket meta; /* ping/ack (metadata) packets */
+        int agreed_pro_version;  /* actually used protocol version */
+        unsigned long last_received; /* in jiffies, either socket */
+        unsigned int ko_count;
+        struct drbd_work  resync_work,
+                          unplug_work,
+                          md_sync_work;
+        struct timer_list resync_timer;
+        struct timer_list md_sync_timer;
+
+        /* Used after attach while negotiating new disk state. */
+        union drbd_state new_state_tmp;
+
+        union drbd_state state;
+        wait_queue_head_t misc_wait;
+        wait_queue_head_t state_wait;  /* upon each state change. */
+        unsigned int send_cnt;
+        unsigned int recv_cnt;
+        unsigned int read_cnt;
+        unsigned int writ_cnt;
+        unsigned int al_writ_cnt;
+        unsigned int bm_writ_cnt;
+        atomic_t ap_bio_cnt;     /* Requests we need to complete */
+        atomic_t ap_pending_cnt; /* AP data packets on the wire, ack expected */
+        atomic_t rs_pending_cnt; /* RS request/data packets on the wire */
+        atomic_t unacked_cnt;    /* Need to send replys for */
+        atomic_t local_cnt;      /* Waiting for local completion */
+        atomic_t net_cnt;        /* Users of net_conf */
+        spinlock_t req_lock;
+        struct drbd_tl_epoch *unused_spare_tle; /* for pre-allocation */
+        struct drbd_tl_epoch *newest_tle;
+        struct drbd_tl_epoch *oldest_tle;
+        struct list_head out_of_sequence_requests;
+        struct hlist_head *tl_hash;
+        unsigned int tl_hash_s;
+
+        /* blocks to sync in this run [unit BM_BLOCK_SIZE] */
+        unsigned long rs_total;
+        /* number of sync IOs that failed in this run */
+        unsigned long rs_failed;
+        /* Syncer's start time [unit jiffies] */
+        unsigned long rs_start;
+        /* cumulated time in PausedSyncX state [unit jiffies] */
+        unsigned long rs_paused;
+        /* block not up-to-date at mark [unit BM_BLOCK_SIZE] */
+        unsigned long rs_mark_left;
+        /* marks's time [unit jiffies] */
+        unsigned long rs_mark_time;
+        /* skipped because csum was equeal [unit BM_BLOCK_SIZE] */
+        unsigned long rs_same_csum;
+
+        /* where does the admin want us to start? (sector) */
+        sector_t ov_start_sector;
+        /* where are we now? (sector) */
+        sector_t ov_position;
+        /* Start sector of out of sync range (to merge printk reporting). */
+        sector_t ov_last_oos_start;
+        /* size of out-of-sync range in sectors. */
+        sector_t ov_last_oos_size;
+        unsigned long ov_left; /* in bits */
+        struct crypto_hash *csums_tfm;
+        struct crypto_hash *verify_tfm;
+
+        struct drbd_thread receiver;
+        struct drbd_thread worker;
+        struct drbd_thread asender;
+        struct drbd_bitmap *bitmap;
+        unsigned long bm_resync_fo; /* bit offset for drbd_bm_find_next */
+
+        /* Used to track operations of resync... */
+        struct lru_cache *resync;
+        /* Number of locked elements in resync LRU */
+        unsigned int resync_locked;
+        /* resync extent number waiting for application requests */
+        unsigned int resync_wenr;
+
+        int open_cnt;
+        u64 *p_uuid;
+        struct drbd_epoch *current_epoch;
+        spinlock_t epoch_lock;
+        unsigned int epochs;
+        enum write_ordering_e write_ordering;
+        struct list_head active_ee; /* IO in progress */
+        struct list_head sync_ee;   /* IO in progress */
+        struct list_head done_ee;   /* send ack */
+        struct list_head read_ee;   /* IO in progress */
+        struct list_head net_ee;    /* zero-copy network send in progress */
+        struct hlist_head *ee_hash; /* is proteced by req_lock! */
+        unsigned int ee_hash_s;
+
+        /* this one is protected by ee_lock, single thread */
+        struct drbd_epoch_entry *last_write_w_barrier;
+
+        int next_barrier_nr;
+        struct hlist_head *app_reads_hash; /* is proteced by req_lock */
+        struct list_head resync_reads;
+        atomic_t pp_in_use;
+        wait_queue_head_t ee_wait;
+        struct page *md_io_page;        /* one page buffer for md_io */
+        struct page *md_io_tmpp;        /* for logical_block_size != 512 */
+        struct mutex md_io_mutex;       /* protects the md_io_buffer */
+        spinlock_t al_lock;
+        wait_queue_head_t al_wait;
+        struct lru_cache *act_log;      /* activity log */
+        unsigned int al_tr_number;
+        int al_tr_cycle;
+        int al_tr_pos;   /* position of the next transaction in the journal */
+        struct crypto_hash *cram_hmac_tfm;
+        struct crypto_hash *integrity_w_tfm; /* to be used by the worker thread */
+        struct crypto_hash *integrity_r_tfm; /* to be used by the receiver thread */
+        void *int_dig_out;
+        void *int_dig_in;
+        void *int_dig_vv;
+        wait_queue_head_t seq_wait;
+        atomic_t packet_seq;
+        unsigned int peer_seq;
+        spinlock_t peer_seq_lock;
+        unsigned int minor;
+        unsigned long comm_bm_set; /* communicated number of set bits. */
+        cpumask_var_t cpu_mask;
+        struct bm_io_work bm_io_work;
+        u64 ed_uuid; /* UUID of the exposed data */
+        struct mutex state_mutex;
+        char congestion_reason;  /* Why we where congested... */
+};
+
+static inline struct drbd_conf *minor_to_mdev(unsigned int minor)
+{
+        struct drbd_conf *mdev;
+
+        mdev = minor < minor_count ? minor_table[minor] : NULL;
+
+        return mdev;
+}
+
+static inline unsigned int mdev_to_minor(struct drbd_conf *mdev)
+{
+        return mdev->minor;
+}
+
+/* returns 1 if it was successfull,
+ * returns 0 if there was no data socket.
+ * so wherever you are going to use the data.socket, e.g. do
+ * if (!drbd_get_data_sock(mdev))
+ *      return 0;
+ *      CODE();
+ * drbd_put_data_sock(mdev);
+ */
+static inline int drbd_get_data_sock(struct drbd_conf *mdev)
+{
+        mutex_lock(&mdev->data.mutex);
+        /* drbd_disconnect() could have called drbd_free_sock()
+         * while we were waiting in down()... */
+        if (unlikely(mdev->data.socket == NULL)) {
+                mutex_unlock(&mdev->data.mutex);
+                return 0;
+        }
+        return 1;
+}
+
+static inline void drbd_put_data_sock(struct drbd_conf *mdev)
+{
+        mutex_unlock(&mdev->data.mutex);
+}
+
+/*
+ * function declarations
+ *************************/
+
+/* drbd_main.c */
+
+enum chg_state_flags {
+        CS_HARD = 1,
+        CS_VERBOSE = 2,
+        CS_WAIT_COMPLETE = 4,
+        CS_SERIALIZE    = 8,
+        CS_ORDERED      = CS_WAIT_COMPLETE + CS_SERIALIZE,
+};
+
+extern void drbd_init_set_defaults(struct drbd_conf *mdev);
+extern int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+                        union drbd_state mask, union drbd_state val);
+extern void drbd_force_state(struct drbd_conf *, union drbd_state,
+                        union drbd_state);
+extern int _drbd_request_state(struct drbd_conf *, union drbd_state,
+                        union drbd_state, enum chg_state_flags);
+extern int __drbd_set_state(struct drbd_conf *, union drbd_state,
+                            enum chg_state_flags, struct completion *done);
+extern void print_st_err(struct drbd_conf *, union drbd_state,
+                        union drbd_state, int);
+extern int  drbd_thread_start(struct drbd_thread *thi);
+extern void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait);
+#ifdef CONFIG_SMP
+extern void drbd_thread_current_set_cpu(struct drbd_conf *mdev);
+extern void drbd_calc_cpu_mask(struct drbd_conf *mdev);
+#else
+#define drbd_thread_current_set_cpu(A) ({})
+#define drbd_calc_cpu_mask(A) ({})
+#endif
+extern void drbd_free_resources(struct drbd_conf *mdev);
+extern void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
+                       unsigned int set_size);
+extern void tl_clear(struct drbd_conf *mdev);
+extern void _tl_add_barrier(struct drbd_conf *, struct drbd_tl_epoch *);
+extern void drbd_free_sock(struct drbd_conf *mdev);
+extern int drbd_send(struct drbd_conf *mdev, struct socket *sock,
+                        void *buf, size_t size, unsigned msg_flags);
+extern int drbd_send_protocol(struct drbd_conf *mdev);
+extern int drbd_send_uuids(struct drbd_conf *mdev);
+extern int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev);
+extern int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val);
+extern int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply);
+extern int _drbd_send_state(struct drbd_conf *mdev);
+extern int drbd_send_state(struct drbd_conf *mdev);
+extern int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
+                        enum drbd_packets cmd, struct p_header *h,
+                        size_t size, unsigned msg_flags);
+#define USE_DATA_SOCKET 1
+#define USE_META_SOCKET 0
+extern int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
+                        enum drbd_packets cmd, struct p_header *h,
+                        size_t size);
+extern int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd,
+                        char *data, size_t size);
+extern int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc);
+extern int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr,
+                        u32 set_size);
+extern int drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
+                        struct drbd_epoch_entry *e);
+extern int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
+                        struct p_block_req *rp);
+extern int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
+                        struct p_data *dp);
+extern int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
+                            sector_t sector, int blksize, u64 block_id);
+extern int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
+                           struct drbd_epoch_entry *e);
+extern int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req);
+extern int _drbd_send_barrier(struct drbd_conf *mdev,
+                        struct drbd_tl_epoch *barrier);
+extern int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
+                              sector_t sector, int size, u64 block_id);
+extern int drbd_send_drequest_csum(struct drbd_conf *mdev,
+                                   sector_t sector,int size,
+                                   void *digest, int digest_size,
+                                   enum drbd_packets cmd);
+extern int drbd_send_ov_request(struct drbd_conf *mdev,sector_t sector,int size);
+
+extern int drbd_send_bitmap(struct drbd_conf *mdev);
+extern int _drbd_send_bitmap(struct drbd_conf *mdev);
+extern int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode);
+extern void drbd_free_bc(struct drbd_backing_dev *ldev);
+extern void drbd_mdev_cleanup(struct drbd_conf *mdev);
+
+/* drbd_meta-data.c (still in drbd_main.c) */
+extern void drbd_md_sync(struct drbd_conf *mdev);
+extern int  drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev);
+/* maybe define them below as inline? */
+extern void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
+extern void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local);
+extern void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
+extern void _drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local);
+extern void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local);
+extern void drbd_md_set_flag(struct drbd_conf *mdev, int flags) __must_hold(local);
+extern void drbd_md_clear_flag(struct drbd_conf *mdev, int flags)__must_hold(local);
+extern int drbd_md_test_flag(struct drbd_backing_dev *, int);
+extern void drbd_md_mark_dirty(struct drbd_conf *mdev);
+extern void drbd_queue_bitmap_io(struct drbd_conf *mdev,
+                                 int (*io_fn)(struct drbd_conf *),
+                                 void (*done)(struct drbd_conf *, int),
+                                 char *why);
+extern int drbd_bmio_set_n_write(struct drbd_conf *mdev);
+extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
+extern int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why);
+
+
+/* Meta data layout
+   We reserve a 128MB Block (4k aligned)
+   * either at the end of the backing device
+   * or on a seperate meta data device. */
+
+#define MD_RESERVED_SECT (128LU << 11)  /* 128 MB, unit sectors */
+/* The following numbers are sectors */
+#define MD_AL_OFFSET 8      /* 8 Sectors after start of meta area */
+#define MD_AL_MAX_SIZE 64   /* = 32 kb LOG  ~ 3776 extents ~ 14 GB Storage */
+/* Allows up to about 3.8TB */
+#define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_MAX_SIZE)
+
+/* Since the smalles IO unit is usually 512 byte */
+#define MD_SECTOR_SHIFT  9
+#define MD_SECTOR_SIZE   (1<<MD_SECTOR_SHIFT)
+
+/* activity log */
+#define AL_EXTENTS_PT ((MD_SECTOR_SIZE-12)/8-1) /* 61 ; Extents per 512B sector */
+#define AL_EXTENT_SHIFT 22               /* One extent represents 4M Storage */
+#define AL_EXTENT_SIZE (1<<AL_EXTENT_SHIFT)
+
+#if BITS_PER_LONG == 32
+#define LN2_BPL 5
+#define cpu_to_lel(A) cpu_to_le32(A)
+#define lel_to_cpu(A) le32_to_cpu(A)
+#elif BITS_PER_LONG == 64
+#define LN2_BPL 6
+#define cpu_to_lel(A) cpu_to_le64(A)
+#define lel_to_cpu(A) le64_to_cpu(A)
+#else
+#error "LN2 of BITS_PER_LONG unknown!"
+#endif
+
+/* resync bitmap */
+/* 16MB sized 'bitmap extent' to track syncer usage */
+struct bm_extent {
+        int rs_left; /* number of bits set (out of sync) in this extent. */
+        int rs_failed; /* number of failed resync requests in this extent. */
+        unsigned long flags;
+        struct lc_element lce;
+};
+
+#define BME_NO_WRITES  0  /* bm_extent.flags: no more requests on this one! */
+#define BME_LOCKED     1  /* bm_extent.flags: syncer active on this one. */
+
+/* drbd_bitmap.c */
+/*
+ * We need to store one bit for a block.
+ * Example: 1GB disk @ 4096 byte blocks ==> we need 32 KB bitmap.
+ * Bit 0 ==> local node thinks this block is binary identical on both nodes
+ * Bit 1 ==> local node thinks this block needs to be synced.
+ */
+
+#define BM_BLOCK_SHIFT  12                       /* 4k per bit */
+#define BM_BLOCK_SIZE    (1<<BM_BLOCK_SHIFT)
+/* (9+3) : 512 bytes @ 8 bits; representing 16M storage
+ * per sector of on disk bitmap */
+#define BM_EXT_SHIFT     (BM_BLOCK_SHIFT + MD_SECTOR_SHIFT + 3)  /* = 24 */
+#define BM_EXT_SIZE      (1<<BM_EXT_SHIFT)
+
+#if (BM_EXT_SHIFT != 24) || (BM_BLOCK_SHIFT != 12)
+#error "HAVE YOU FIXED drbdmeta AS WELL??"
+#endif
+
+/* thus many _storage_ sectors are described by one bit */
+#define BM_SECT_TO_BIT(x)   ((x)>>(BM_BLOCK_SHIFT-9))
+#define BM_BIT_TO_SECT(x)   ((sector_t)(x)<<(BM_BLOCK_SHIFT-9))
+#define BM_SECT_PER_BIT     BM_BIT_TO_SECT(1)
+
+/* bit to represented kilo byte conversion */
+#define Bit2KB(bits) ((bits)<<(BM_BLOCK_SHIFT-10))
+
+/* in which _bitmap_ extent (resp. sector) the bit for a certain
+ * _storage_ sector is located in */
+#define BM_SECT_TO_EXT(x)   ((x)>>(BM_EXT_SHIFT-9))
+
+/* how much _storage_ sectors we have per bitmap sector */
+#define BM_EXT_TO_SECT(x)   ((sector_t)(x) << (BM_EXT_SHIFT-9))
+#define BM_SECT_PER_EXT     BM_EXT_TO_SECT(1)
+
+/* in one sector of the bitmap, we have this many activity_log extents. */
+#define AL_EXT_PER_BM_SECT  (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
+#define BM_WORDS_PER_AL_EXT (1 << (AL_EXTENT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
+
+#define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
+#define BM_BLOCKS_PER_BM_EXT_MASK  ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
+
+/* the extent in "PER_EXTENT" below is an activity log extent
+ * we need that many (long words/bytes) to store the bitmap
+ *                   of one AL_EXTENT_SIZE chunk of storage.
+ * we can store the bitmap for that many AL_EXTENTS within
+ * one sector of the _on_disk_ bitmap:
+ * bit   0        bit 37   bit 38            bit (512*8)-1
+ *           ...|........|........|.. // ..|........|
+ * sect. 0       `296     `304                     ^(512*8*8)-1
+ *
+#define BM_WORDS_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / BITS_PER_LONG )
+#define BM_BYTES_PER_EXT    ( (AL_EXT_SIZE/BM_BLOCK_SIZE) / 8 )  // 128
+#define BM_EXT_PER_SECT     ( 512 / BM_BYTES_PER_EXTENT )        //   4
+ */
+
+#define DRBD_MAX_SECTORS_32 (0xffffffffLU)
+#define DRBD_MAX_SECTORS_BM \
+          ((MD_RESERVED_SECT - MD_BM_OFFSET) * (1LL<<(BM_EXT_SHIFT-9)))
+#if DRBD_MAX_SECTORS_BM < DRBD_MAX_SECTORS_32
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
+#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_BM
+#elif !defined(CONFIG_LBD) && BITS_PER_LONG == 32
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_32
+#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_32
+#else
+#define DRBD_MAX_SECTORS      DRBD_MAX_SECTORS_BM
+/* 16 TB in units of sectors */
+#if BITS_PER_LONG == 32
+/* adjust by one page worth of bitmap,
+ * so we won't wrap around in drbd_bm_find_next_bit.
+ * you should use 64bit OS for that much storage, anyways. */
+#define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0xffff7fff)
+#else
+#define DRBD_MAX_SECTORS_FLEX BM_BIT_TO_SECT(0x1LU << 32)
+#endif
+#endif
+
+/* Sector shift value for the "hash" functions of tl_hash and ee_hash tables.
+ * With a value of 6 all IO in one 32K block make it to the same slot of the
+ * hash table. */
+#define HT_SHIFT 6
+#define DRBD_MAX_SEGMENT_SIZE (1U<<(9+HT_SHIFT))
+
+/* Number of elements in the app_reads_hash */
+#define APP_R_HSIZE 15
+
+extern int  drbd_bm_init(struct drbd_conf *mdev);
+extern int  drbd_bm_resize(struct drbd_conf *mdev, sector_t sectors);
+extern void drbd_bm_cleanup(struct drbd_conf *mdev);
+extern void drbd_bm_set_all(struct drbd_conf *mdev);
+extern void drbd_bm_clear_all(struct drbd_conf *mdev);
+extern int  drbd_bm_set_bits(
+                struct drbd_conf *mdev, unsigned long s, unsigned long e);
+extern int  drbd_bm_clear_bits(
+                struct drbd_conf *mdev, unsigned long s, unsigned long e);
+/* bm_set_bits variant for use while holding drbd_bm_lock */
+extern void _drbd_bm_set_bits(struct drbd_conf *mdev,
+                const unsigned long s, const unsigned long e);
+extern int  drbd_bm_test_bit(struct drbd_conf *mdev, unsigned long bitnr);
+extern int  drbd_bm_e_weight(struct drbd_conf *mdev, unsigned long enr);
+extern int  drbd_bm_write_sect(struct drbd_conf *mdev, unsigned long enr) __must_hold(local);
+extern int  drbd_bm_read(struct drbd_conf *mdev) __must_hold(local);
+extern int  drbd_bm_write(struct drbd_conf *mdev) __must_hold(local);
+extern unsigned long drbd_bm_ALe_set_all(struct drbd_conf *mdev,
+                unsigned long al_enr);
+extern size_t        drbd_bm_words(struct drbd_conf *mdev);
+extern unsigned long drbd_bm_bits(struct drbd_conf *mdev);
+extern sector_t      drbd_bm_capacity(struct drbd_conf *mdev);
+extern unsigned long drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
+/* bm_find_next variants for use while you hold drbd_bm_lock() */
+extern unsigned long _drbd_bm_find_next(struct drbd_conf *mdev, unsigned long bm_fo);
+extern unsigned long _drbd_bm_find_next_zero(struct drbd_conf *mdev, unsigned long bm_fo);
+extern unsigned long drbd_bm_total_weight(struct drbd_conf *mdev);
+extern int drbd_bm_rs_done(struct drbd_conf *mdev);
+/* for receive_bitmap */
+extern void drbd_bm_merge_lel(struct drbd_conf *mdev, size_t offset,
+                size_t number, unsigned long *buffer);
+/* for _drbd_send_bitmap and drbd_bm_write_sect */
+extern void drbd_bm_get_lel(struct drbd_conf *mdev, size_t offset,
+                size_t number, unsigned long *buffer);
+
+extern void drbd_bm_lock(struct drbd_conf *mdev, char *why);
+extern void drbd_bm_unlock(struct drbd_conf *mdev);
+
+extern int drbd_bm_count_bits(struct drbd_conf *mdev, const unsigned long s, const unsigned long e);
+/* drbd_main.c */
+
+extern struct kmem_cache *drbd_request_cache;
+extern struct kmem_cache *drbd_ee_cache;        /* epoch entries */
+extern struct kmem_cache *drbd_bm_ext_cache;    /* bitmap extents */
+extern struct kmem_cache *drbd_al_ext_cache;    /* activity log extents */
+extern mempool_t *drbd_request_mempool;
+extern mempool_t *drbd_ee_mempool;
+
+extern struct page *drbd_pp_pool; /* drbd's page pool */
+extern spinlock_t   drbd_pp_lock;
+extern int          drbd_pp_vacant;
+extern wait_queue_head_t drbd_pp_wait;
+
+extern rwlock_t global_state_lock;
+
+extern struct drbd_conf *drbd_new_device(unsigned int minor);
+extern void drbd_free_mdev(struct drbd_conf *mdev);
+
+extern int proc_details;
+
+/* drbd_req */
+extern int drbd_make_request_26(struct request_queue *q, struct bio *bio);
+extern int drbd_read_remote(struct drbd_conf *mdev, struct drbd_request *req);
+extern int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec);
+extern int is_valid_ar_handle(struct drbd_request *, sector_t);
+
+
+/* drbd_nl.c */
+extern void drbd_suspend_io(struct drbd_conf *mdev);
+extern void drbd_resume_io(struct drbd_conf *mdev);
+extern char *ppsize(char *buf, unsigned long long size);
+extern sector_t drbd_new_dev_size(struct drbd_conf *,
+                struct drbd_backing_dev *);
+enum determine_dev_size { dev_size_error = -1, unchanged = 0, shrunk = 1, grew = 2 };
+extern enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *) __must_hold(local);
+extern void resync_after_online_grow(struct drbd_conf *);
+extern void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int) __must_hold(local);
+extern int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role,
+                int force);
+enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev);
+extern int drbd_khelper(struct drbd_conf *mdev, char *cmd);
+
+/* drbd_worker.c */
+extern int drbd_worker(struct drbd_thread *thi);
+extern int drbd_alter_sa(struct drbd_conf *mdev, int na);
+extern void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side);
+extern void resume_next_sg(struct drbd_conf *mdev);
+extern void suspend_other_sg(struct drbd_conf *mdev);
+extern int drbd_resync_finished(struct drbd_conf *mdev);
+/* maybe rather drbd_main.c ? */
+extern int drbd_md_sync_page_io(struct drbd_conf *mdev,
+                struct drbd_backing_dev *bdev, sector_t sector, int rw);
+extern void drbd_ov_oos_found(struct drbd_conf*, sector_t, int);
+
+static inline void ov_oos_print(struct drbd_conf *mdev)
+{
+        if (mdev->ov_last_oos_size) {
+                dev_err(DEV, "Out of sync: start=%llu, size=%lu (sectors)\n",
+                     (unsigned long long)mdev->ov_last_oos_start,
+                     (unsigned long)mdev->ov_last_oos_size);
+        }
+        mdev->ov_last_oos_size=0;
+}
+
+
+extern void drbd_csum(struct drbd_conf *, struct crypto_hash *, struct bio *, void *);
+/* worker callbacks */
+extern int w_req_cancel_conflict(struct drbd_conf *, struct drbd_work *, int);
+extern int w_read_retry_remote(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_data_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_rsdata_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_csum_rs_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_ov_reply(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_end_ov_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_ov_finished(struct drbd_conf *, struct drbd_work *, int);
+extern int w_resync_inactive(struct drbd_conf *, struct drbd_work *, int);
+extern int w_resume_next_sg(struct drbd_conf *, struct drbd_work *, int);
+extern int w_io_error(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_write_hint(struct drbd_conf *, struct drbd_work *, int);
+extern int w_make_resync_request(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_dblock(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_barrier(struct drbd_conf *, struct drbd_work *, int);
+extern int w_send_read_req(struct drbd_conf *, struct drbd_work *, int);
+extern int w_prev_work_done(struct drbd_conf *, struct drbd_work *, int);
+extern int w_e_reissue(struct drbd_conf *, struct drbd_work *, int);
+
+extern void resync_timer_fn(unsigned long data);
+
+/* drbd_receiver.c */
+extern int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list);
+extern struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
+                                            u64 id,
+                                            sector_t sector,
+                                            unsigned int data_size,
+                                            gfp_t gfp_mask) __must_hold(local);
+extern void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e);
+extern void drbd_wait_ee_list_empty(struct drbd_conf *mdev,
+                struct list_head *head);
+extern void _drbd_wait_ee_list_empty(struct drbd_conf *mdev,
+                struct list_head *head);
+extern void drbd_set_recv_tcq(struct drbd_conf *mdev, int tcq_enabled);
+extern void _drbd_clear_done_ee(struct drbd_conf *mdev, struct list_head *to_be_freed);
+extern void drbd_flush_workqueue(struct drbd_conf *mdev);
+
+/* yes, there is kernel_setsockopt, but only since 2.6.18. we don't need to
+ * mess with get_fs/set_fs, we know we are KERNEL_DS always. */
+static inline int drbd_setsockopt(struct socket *sock, int level, int optname,
+                        char __user *optval, int optlen)
+{
+        int err;
+        if (level == SOL_SOCKET)
+                err = sock_setsockopt(sock, level, optname, optval, optlen);
+        else
+                err = sock->ops->setsockopt(sock, level, optname, optval,
+                                            optlen);
+        return err;
+}
+
+static inline void drbd_tcp_cork(struct socket *sock)
+{
+        int __user val = 1;
+        (void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
+                        (char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_uncork(struct socket *sock)
+{
+        int __user val = 0;
+        (void) drbd_setsockopt(sock, SOL_TCP, TCP_CORK,
+                        (char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_nodelay(struct socket *sock)
+{
+        int __user val = 1;
+        (void) drbd_setsockopt(sock, SOL_TCP, TCP_NODELAY,
+                        (char __user *)&val, sizeof(val));
+}
+
+static inline void drbd_tcp_quickack(struct socket *sock)
+{
+        int __user val = 1;
+        (void) drbd_setsockopt(sock, SOL_TCP, TCP_QUICKACK,
+                        (char __user *)&val, sizeof(val));
+}
+
+void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo);
+
+/* drbd_proc.c */
+extern struct proc_dir_entry *drbd_proc;
+extern struct file_operations drbd_proc_fops;
+extern const char *drbd_conn_str(enum drbd_conns s);
+extern const char *drbd_role_str(enum drbd_role s);
+
+/* drbd_actlog.c */
+extern void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_al_complete_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_rs_complete_io(struct drbd_conf *mdev, sector_t sector);
+extern int drbd_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern int drbd_try_rs_begin_io(struct drbd_conf *mdev, sector_t sector);
+extern void drbd_rs_cancel_all(struct drbd_conf *mdev);
+extern int drbd_rs_del_all(struct drbd_conf *mdev);
+extern void drbd_rs_failed_io(struct drbd_conf *mdev,
+                sector_t sector, int size);
+extern int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *);
+extern void __drbd_set_in_sync(struct drbd_conf *mdev, sector_t sector,
+                int size, const char *file, const unsigned int line);
+#define drbd_set_in_sync(mdev, sector, size) \
+        __drbd_set_in_sync(mdev, sector, size, __FILE__, __LINE__)
+extern void __drbd_set_out_of_sync(struct drbd_conf *mdev, sector_t sector,
+                int size, const char *file, const unsigned int line);
+#define drbd_set_out_of_sync(mdev, sector, size) \
+        __drbd_set_out_of_sync(mdev, sector, size, __FILE__, __LINE__)
+extern void drbd_al_apply_to_bm(struct drbd_conf *mdev);
+extern void drbd_al_to_on_disk_bm(struct drbd_conf *mdev);
+extern void drbd_al_shrink(struct drbd_conf *mdev);
+
+
+/* drbd_nl.c */
+
+void drbd_nl_cleanup(void);
+int __init drbd_nl_init(void);
+void drbd_bcast_state(struct drbd_conf *mdev, union drbd_state);
+void drbd_bcast_sync_progress(struct drbd_conf *mdev);
+void drbd_bcast_ee(struct drbd_conf *mdev,
+                const char *reason, const int dgs,
+                const char* seen_hash, const char* calc_hash,
+                const struct drbd_epoch_entry* e);
+
+
+/**
+ * DOC: DRBD State macros
+ *
+ * These macros are used to express state changes in easily readable form.
+ *
+ * The NS macros expand to a mask and a value, that can be bit ored onto the
+ * current state as soon as the spinlock (req_lock) was taken.
+ *
+ * The _NS macros are used for state functions that get called with the
+ * spinlock. These macros expand directly to the new state value.
+ *
+ * Besides the basic forms NS() and _NS() additional _?NS[23] are defined
+ * to express state changes that affect more than one aspect of the state.
+ *
+ * E.g. NS2(conn, C_CONNECTED, peer, R_SECONDARY)
+ * Means that the network connection was established and that the peer
+ * is in secondary role.
+ */
+#define role_MASK R_MASK
+#define peer_MASK R_MASK
+#define disk_MASK D_MASK
+#define pdsk_MASK D_MASK
+#define conn_MASK C_MASK
+#define susp_MASK 1
+#define user_isp_MASK 1
+#define aftr_isp_MASK 1
+
+#define NS(T, S) \
+        ({ union drbd_state mask; mask.i = 0; mask.T = T##_MASK; mask; }), \
+        ({ union drbd_state val; val.i = 0; val.T = (S); val; })
+#define NS2(T1, S1, T2, S2) \
+        ({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
+          mask.T2 = T2##_MASK; mask; }), \
+        ({ union drbd_state val; val.i = 0; val.T1 = (S1); \
+          val.T2 = (S2); val; })
+#define NS3(T1, S1, T2, S2, T3, S3) \
+        ({ union drbd_state mask; mask.i = 0; mask.T1 = T1##_MASK; \
+          mask.T2 = T2##_MASK; mask.T3 = T3##_MASK; mask; }), \
+        ({ union drbd_state val;  val.i = 0; val.T1 = (S1); \
+          val.T2 = (S2); val.T3 = (S3); val; })
+
+#define _NS(D, T, S) \
+        D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T = (S); __ns; })
+#define _NS2(D, T1, S1, T2, S2) \
+        D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
+        __ns.T2 = (S2); __ns; })
+#define _NS3(D, T1, S1, T2, S2, T3, S3) \
+        D, ({ union drbd_state __ns; __ns.i = D->state.i; __ns.T1 = (S1); \
+        __ns.T2 = (S2); __ns.T3 = (S3); __ns; })
+
+/*
+ * inline helper functions
+ *************************/
+
+static inline void drbd_state_lock(struct drbd_conf *mdev)
+{
+        wait_event(mdev->misc_wait,
+                   !test_and_set_bit(CLUSTER_ST_CHANGE, &mdev->flags));
+}
+
+static inline void drbd_state_unlock(struct drbd_conf *mdev)
+{
+        clear_bit(CLUSTER_ST_CHANGE, &mdev->flags);
+        wake_up(&mdev->misc_wait);
+}
+
+static inline int _drbd_set_state(struct drbd_conf *mdev,
+                                   union drbd_state ns, enum chg_state_flags flags,
+                                   struct completion *done)
+{
+        int rv;
+
+        read_lock(&global_state_lock);
+        rv = __drbd_set_state(mdev, ns, flags, done);
+        read_unlock(&global_state_lock);
+
+        return rv;
+}
+
+/**
+ * drbd_request_state() - Reqest a state change
+ * @mdev:       DRBD device.
+ * @mask:       mask of state bits to change.
+ * @val:        value of new state bits.
+ *
+ * This is the most graceful way of requesting a state change. It is verbose
+ * quite verbose in case the state change is not possible, and all those
+ * state changes are globally serialized.
+ */
+static inline int drbd_request_state(struct drbd_conf *mdev,
+                                     union drbd_state mask,
+                                     union drbd_state val)
+{
+        return _drbd_request_state(mdev, mask, val, CS_VERBOSE + CS_ORDERED);
+}
+
+#define __drbd_chk_io_error(m,f) __drbd_chk_io_error_(m,f, __func__)
+static inline void __drbd_chk_io_error_(struct drbd_conf *mdev, int forcedetach, const char *where)
+{
+        switch (mdev->ldev->dc.on_io_error) {
+        case EP_PASS_ON:
+                if (!forcedetach) {
+                        if (printk_ratelimit())
+                                dev_err(DEV, "Local IO failed in %s."
+                                             "Passing error on...\n", where);
+                        break;
+                }
+                /* NOTE fall through to detach case if forcedetach set */
+        case EP_DETACH:
+        case EP_CALL_HELPER:
+                if (mdev->state.disk > D_FAILED) {
+                        _drbd_set_state(_NS(mdev, disk, D_FAILED), CS_HARD, NULL);
+                        dev_err(DEV, "Local IO failed in %s."
+                                     "Detaching...\n", where);
+                }
+                break;
+        }
+}
+
+/**
+ * drbd_chk_io_error: Handle the on_io_error setting, should be called from all io completion handlers
+ * @mdev:        DRBD device.
+ * @error:       Error code passed to the IO completion callback
+ * @forcedetach: Force detach. I.e. the error happened while accessing the meta data
+ *
+ * See also drbd_main.c:after_state_ch() if (os.disk > D_FAILED && ns.disk == D_FAILED)
+ */
+#define drbd_chk_io_error(m,e,f) drbd_chk_io_error_(m,e,f, __func__)
+static inline void drbd_chk_io_error_(struct drbd_conf *mdev,
+        int error, int forcedetach, const char *where)
+{
+        if (error) {
+                unsigned long flags;
+                spin_lock_irqsave(&mdev->req_lock, flags);
+                __drbd_chk_io_error_(mdev, forcedetach, where);
+                spin_unlock_irqrestore(&mdev->req_lock, flags);
+        }
+}
+
+
+/**
+ * drbd_md_first_sector() - Returns the first sector number of the meta data area
+ * @bdev:       Meta data block device.
+ *
+ * BTW, for internal meta data, this happens to be the maximum capacity
+ * we could agree upon with our peer node.
+ */
+static inline sector_t drbd_md_first_sector(struct drbd_backing_dev *bdev)
+{
+        switch (bdev->dc.meta_dev_idx) {
+        case DRBD_MD_INDEX_INTERNAL:
+        case DRBD_MD_INDEX_FLEX_INT:
+                return bdev->md.md_offset + bdev->md.bm_offset;
+        case DRBD_MD_INDEX_FLEX_EXT:
+        default:
+                return bdev->md.md_offset;
+        }
+}
+
+/**
+ * drbd_md_last_sector() - Return the last sector number of the meta data area
+ * @bdev:       Meta data block device.
+ */
+static inline sector_t drbd_md_last_sector(struct drbd_backing_dev *bdev)
+{
+        switch (bdev->dc.meta_dev_idx) {
+        case DRBD_MD_INDEX_INTERNAL:
+        case DRBD_MD_INDEX_FLEX_INT:
+                return bdev->md.md_offset + MD_AL_OFFSET - 1;
+        case DRBD_MD_INDEX_FLEX_EXT:
+        default:
+                return bdev->md.md_offset + bdev->md.md_size_sect;
+        }
+}
+
+/* Returns the number of 512 byte sectors of the device */
+static inline sector_t drbd_get_capacity(struct block_device *bdev)
+{
+        /* return bdev ? get_capacity(bdev->bd_disk) : 0; */
+        return bdev ? bdev->bd_inode->i_size >> 9 : 0;
+}
+
+/**
+ * drbd_get_max_capacity() - Returns the capacity we announce to out peer
+ * @bdev:       Meta data block device.
+ *
+ * returns the capacity we announce to out peer.  we clip ourselves at the
+ * various MAX_SECTORS, because if we don't, current implementation will
+ * oops sooner or later
+ */
+static inline sector_t drbd_get_max_capacity(struct drbd_backing_dev *bdev)
+{
+        sector_t s;
+        switch (bdev->dc.meta_dev_idx) {
+        case DRBD_MD_INDEX_INTERNAL:
+        case DRBD_MD_INDEX_FLEX_INT:
+                s = drbd_get_capacity(bdev->backing_bdev)
+                        ? min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
+                                        drbd_md_first_sector(bdev))
+                        : 0;
+                break;
+        case DRBD_MD_INDEX_FLEX_EXT:
+                s = min_t(sector_t, DRBD_MAX_SECTORS_FLEX,
+                                drbd_get_capacity(bdev->backing_bdev));
+                /* clip at maximum size the meta device can support */
+                s = min_t(sector_t, s,
+                        BM_EXT_TO_SECT(bdev->md.md_size_sect
+                                     - bdev->md.bm_offset));
+                break;
+        default:
+                s = min_t(sector_t, DRBD_MAX_SECTORS,
+                                drbd_get_capacity(bdev->backing_bdev));
+        }
+        return s;
+}
+
+/**
+ * drbd_md_ss__() - Return the sector number of our meta data super block
+ * @mdev:       DRBD device.
+ * @bdev:       Meta data block device.
+ */
+static inline sector_t drbd_md_ss__(struct drbd_conf *mdev,
+                                    struct drbd_backing_dev *bdev)
+{
+        switch (bdev->dc.meta_dev_idx) {
+        default: /* external, some index */
+                return MD_RESERVED_SECT * bdev->dc.meta_dev_idx;
+        case DRBD_MD_INDEX_INTERNAL:
+                /* with drbd08, internal meta data is always "flexible" */
+        case DRBD_MD_INDEX_FLEX_INT:
+                /* sizeof(struct md_on_disk_07) == 4k
+                 * position: last 4k aligned block of 4k size */
+                if (!bdev->backing_bdev) {
+                        if (__ratelimit(&drbd_ratelimit_state)) {
+                                dev_err(DEV, "bdev->backing_bdev==NULL\n");
+                                dump_stack();
+                        }
+                        return 0;
+                }
+                return (drbd_get_capacity(bdev->backing_bdev) & ~7ULL)
+                        - MD_AL_OFFSET;
+        case DRBD_MD_INDEX_FLEX_EXT:
+                return 0;
+        }
+}
+
+static inline void
+_drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+{
+        list_add_tail(&w->list, &q->q);
+        up(&q->s);
+}
+
+static inline void
+drbd_queue_work_front(struct drbd_work_queue *q, struct drbd_work *w)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&q->q_lock, flags);
+        list_add(&w->list, &q->q);
+        up(&q->s); /* within the spinlock,
+                      see comment near end of drbd_worker() */
+        spin_unlock_irqrestore(&q->q_lock, flags);
+}
+
+static inline void
+drbd_queue_work(struct drbd_work_queue *q, struct drbd_work *w)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&q->q_lock, flags);
+        list_add_tail(&w->list, &q->q);
+        up(&q->s); /* within the spinlock,
+                      see comment near end of drbd_worker() */
+        spin_unlock_irqrestore(&q->q_lock, flags);
+}
+
+static inline void wake_asender(struct drbd_conf *mdev)
+{
+        if (test_bit(SIGNAL_ASENDER, &mdev->flags))
+                force_sig(DRBD_SIG, mdev->asender.task);
+}
+
+static inline void request_ping(struct drbd_conf *mdev)
+{
+        set_bit(SEND_PING, &mdev->flags);
+        wake_asender(mdev);
+}
+
+static inline int drbd_send_short_cmd(struct drbd_conf *mdev,
+        enum drbd_packets cmd)
+{
+        struct p_header h;
+        return drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd, &h, sizeof(h));
+}
+
+static inline int drbd_send_ping(struct drbd_conf *mdev)
+{
+        struct p_header h;
+        return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING, &h, sizeof(h));
+}
+
+static inline int drbd_send_ping_ack(struct drbd_conf *mdev)
+{
+        struct p_header h;
+        return drbd_send_cmd(mdev, USE_META_SOCKET, P_PING_ACK, &h, sizeof(h));
+}
+
+static inline void drbd_thread_stop(struct drbd_thread *thi)
+{
+        _drbd_thread_stop(thi, FALSE, TRUE);
+}
+
+static inline void drbd_thread_stop_nowait(struct drbd_thread *thi)
+{
+        _drbd_thread_stop(thi, FALSE, FALSE);
+}
+
+static inline void drbd_thread_restart_nowait(struct drbd_thread *thi)
+{
+        _drbd_thread_stop(thi, TRUE, FALSE);
+}
+
+/* counts how many answer packets packets we expect from our peer,
+ * for either explicit application requests,
+ * or implicit barrier packets as necessary.
+ * increased:
+ *  w_send_barrier
+ *  _req_mod(req, queue_for_net_write or queue_for_net_read);
+ *    it is much easier and equally valid to count what we queue for the
+ *    worker, even before it actually was queued or send.
+ *    (drbd_make_request_common; recovery path on read io-error)
+ * decreased:
+ *  got_BarrierAck (respective tl_clear, tl_clear_barrier)
+ *  _req_mod(req, data_received)
+ *     [from receive_DataReply]
+ *  _req_mod(req, write_acked_by_peer or recv_acked_by_peer or neg_acked)
+ *     [from got_BlockAck (P_WRITE_ACK, P_RECV_ACK)]
+ *     for some reason it is NOT decreased in got_NegAck,
+ *     but in the resulting cleanup code from report_params.
+ *     we should try to remember the reason for that...
+ *  _req_mod(req, send_failed or send_canceled)
+ *  _req_mod(req, connection_lost_while_pending)
+ *     [from tl_clear_barrier]
+ */
+static inline void inc_ap_pending(struct drbd_conf *mdev)
+{
+        atomic_inc(&mdev->ap_pending_cnt);
+}
+
+#define ERR_IF_CNT_IS_NEGATIVE(which)                           \
+        if (atomic_read(&mdev->which) < 0)                      \
+                dev_err(DEV, "in %s:%d: " #which " = %d < 0 !\n",       \
+                    __func__ , __LINE__ ,                       \
+                    atomic_read(&mdev->which))
+
+#define dec_ap_pending(mdev)    do {                            \
+        typecheck(struct drbd_conf *, mdev);                    \
+        if (atomic_dec_and_test(&mdev->ap_pending_cnt))         \
+                wake_up(&mdev->misc_wait);                      \
+        ERR_IF_CNT_IS_NEGATIVE(ap_pending_cnt); } while (0)
+
+/* counts how many resync-related answers we still expect from the peer
+ *                   increase                   decrease
+ * C_SYNC_TARGET sends P_RS_DATA_REQUEST (and expects P_RS_DATA_REPLY)
+ * C_SYNC_SOURCE sends P_RS_DATA_REPLY   (and expects P_WRITE_ACK whith ID_SYNCER)
+ *                                         (or P_NEG_ACK with ID_SYNCER)
+ */
+static inline void inc_rs_pending(struct drbd_conf *mdev)
+{
+        atomic_inc(&mdev->rs_pending_cnt);
+}
+
+#define dec_rs_pending(mdev)    do {                            \
+        typecheck(struct drbd_conf *, mdev);                    \
+        atomic_dec(&mdev->rs_pending_cnt);                      \
+        ERR_IF_CNT_IS_NEGATIVE(rs_pending_cnt); } while (0)
+
+/* counts how many answers we still need to send to the peer.
+ * increased on
+ *  receive_Data        unless protocol A;
+ *                      we need to send a P_RECV_ACK (proto B)
+ *                      or P_WRITE_ACK (proto C)
+ *  receive_RSDataReply (recv_resync_read) we need to send a P_WRITE_ACK
+ *  receive_DataRequest (receive_RSDataRequest) we need to send back P_DATA
+ *  receive_Barrier_*   we need to send a P_BARRIER_ACK
+ */
+static inline void inc_unacked(struct drbd_conf *mdev)
+{
+        atomic_inc(&mdev->unacked_cnt);
+}
+
+#define dec_unacked(mdev)       do {                            \
+        typecheck(struct drbd_conf *, mdev);                    \
+        atomic_dec(&mdev->unacked_cnt);                         \
+        ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
+
+#define sub_unacked(mdev, n)    do {                            \
+        typecheck(struct drbd_conf *, mdev);                    \
+        atomic_sub(n, &mdev->unacked_cnt);                      \
+        ERR_IF_CNT_IS_NEGATIVE(unacked_cnt); } while (0)
+
+
+static inline void put_net_conf(struct drbd_conf *mdev)
+{
+        if (atomic_dec_and_test(&mdev->net_cnt))
+                wake_up(&mdev->misc_wait);
+}
+
+/**
+ * get_net_conf() - Increase ref count on mdev->net_conf; Returns 0 if nothing there
+ * @mdev:       DRBD device.
+ *
+ * You have to call put_net_conf() when finished working with mdev->net_conf.
+ */
+static inline int get_net_conf(struct drbd_conf *mdev)
+{
+        int have_net_conf;
+
+        atomic_inc(&mdev->net_cnt);
+        have_net_conf = mdev->state.conn >= C_UNCONNECTED;
+        if (!have_net_conf)
+                put_net_conf(mdev);
+        return have_net_conf;
+}
+
+/**
+ * get_ldev() - Increase the ref count on mdev->ldev. Returns 0 if there is no ldev
+ * @M:          DRBD device.
+ *
+ * You have to call put_ldev() when finished working with mdev->ldev.
+ */
+#define get_ldev(M) __cond_lock(local, _get_ldev_if_state(M,D_INCONSISTENT))
+#define get_ldev_if_state(M,MINS) __cond_lock(local, _get_ldev_if_state(M,MINS))
+
+static inline void put_ldev(struct drbd_conf *mdev)
+{
+        __release(local);
+        if (atomic_dec_and_test(&mdev->local_cnt))
+                wake_up(&mdev->misc_wait);
+        D_ASSERT(atomic_read(&mdev->local_cnt) >= 0);
+}
+
+#ifndef __CHECKER__
+static inline int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
+{
+        int io_allowed;
+
+        atomic_inc(&mdev->local_cnt);
+        io_allowed = (mdev->state.disk >= mins);
+        if (!io_allowed)
+                put_ldev(mdev);
+        return io_allowed;
+}
+#else
+extern int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins);
+#endif
+
+/* you must have an "get_ldev" reference */
+static inline void drbd_get_syncer_progress(struct drbd_conf *mdev,
+                unsigned long *bits_left, unsigned int *per_mil_done)
+{
+        /*
+         * this is to break it at compile time when we change that
+         * (we may feel 4TB maximum storage per drbd is not enough)
+         */
+        typecheck(unsigned long, mdev->rs_total);
+
+        /* note: both rs_total and rs_left are in bits, i.e. in
+         * units of BM_BLOCK_SIZE.
+         * for the percentage, we don't care. */
+
+        *bits_left = drbd_bm_total_weight(mdev) - mdev->rs_failed;
+        /* >> 10 to prevent overflow,
+         * +1 to prevent division by zero */
+        if (*bits_left > mdev->rs_total) {
+                /* doh. maybe a logic bug somewhere.
+                 * may also be just a race condition
+                 * between this and a disconnect during sync.
+                 * for now, just prevent in-kernel buffer overflow.
+                 */
+                smp_rmb();
+                dev_warn(DEV, "cs:%s rs_left=%lu > rs_total=%lu (rs_failed %lu)\n",
+                                drbd_conn_str(mdev->state.conn),
+                                *bits_left, mdev->rs_total, mdev->rs_failed);
+                *per_mil_done = 0;
+        } else {
+                /* make sure the calculation happens in long context */
+                unsigned long tmp = 1000UL -
+                                (*bits_left >> 10)*1000UL
+                                / ((mdev->rs_total >> 10) + 1UL);
+                *per_mil_done = tmp;
+        }
+}
+
+
+/* this throttles on-the-fly application requests
+ * according to max_buffers settings;
+ * maybe re-implement using semaphores? */
+static inline int drbd_get_max_buffers(struct drbd_conf *mdev)
+{
+        int mxb = 1000000; /* arbitrary limit on open requests */
+        if (get_net_conf(mdev)) {
+                mxb = mdev->net_conf->max_buffers;
+                put_net_conf(mdev);
+        }
+        return mxb;
+}
+
+static inline int drbd_state_is_stable(union drbd_state s)
+{
+
+        /* DO NOT add a default clause, we want the compiler to warn us
+         * for any newly introduced state we may have forgotten to add here */
+
+        switch ((enum drbd_conns)s.conn) {
+        /* new io only accepted when there is no connection, ... */
+        case C_STANDALONE:
+        case C_WF_CONNECTION:
+        /* ... or there is a well established connection. */
+        case C_CONNECTED:
+        case C_SYNC_SOURCE:
+        case C_SYNC_TARGET:
+        case C_VERIFY_S:
+        case C_VERIFY_T:
+        case C_PAUSED_SYNC_S:
+        case C_PAUSED_SYNC_T:
+                /* maybe stable, look at the disk state */
+                break;
+
+        /* no new io accepted during tansitional states
+         * like handshake or teardown */
+        case C_DISCONNECTING:
+        case C_UNCONNECTED:
+        case C_TIMEOUT:
+        case C_BROKEN_PIPE:
+        case C_NETWORK_FAILURE:
+        case C_PROTOCOL_ERROR:
+        case C_TEAR_DOWN:
+        case C_WF_REPORT_PARAMS:
+        case C_STARTING_SYNC_S:
+        case C_STARTING_SYNC_T:
+        case C_WF_BITMAP_S:
+        case C_WF_BITMAP_T:
+        case C_WF_SYNC_UUID:
+        case C_MASK:
+                /* not "stable" */
+                return 0;
+        }
+
+        switch ((enum drbd_disk_state)s.disk) {
+        case D_DISKLESS:
+        case D_INCONSISTENT:
+        case D_OUTDATED:
+        case D_CONSISTENT:
+        case D_UP_TO_DATE:
+                /* disk state is stable as well. */
+                break;
+
+        /* no new io accepted during tansitional states */
+        case D_ATTACHING:
+        case D_FAILED:
+        case D_NEGOTIATING:
+        case D_UNKNOWN:
+        case D_MASK:
+                /* not "stable" */
+                return 0;
+        }
+
+        return 1;
+}
+
+static inline int __inc_ap_bio_cond(struct drbd_conf *mdev)
+{
+        int mxb = drbd_get_max_buffers(mdev);
+
+        if (mdev->state.susp)
+                return 0;
+        if (test_bit(SUSPEND_IO, &mdev->flags))
+                return 0;
+
+        /* to avoid potential deadlock or bitmap corruption,
+         * in various places, we only allow new application io
+         * to start during "stable" states. */
+
+        /* no new io accepted when attaching or detaching the disk */
+        if (!drbd_state_is_stable(mdev->state))
+                return 0;
+
+        /* since some older kernels don't have atomic_add_unless,
+         * and we are within the spinlock anyways, we have this workaround.  */
+        if (atomic_read(&mdev->ap_bio_cnt) > mxb)
+                return 0;
+        if (test_bit(BITMAP_IO, &mdev->flags))
+                return 0;
+        return 1;
+}
+
+/* I'd like to use wait_event_lock_irq,
+ * but I'm not sure when it got introduced,
+ * and not sure when it has 3 or 4 arguments */
+static inline void inc_ap_bio(struct drbd_conf *mdev, int one_or_two)
+{
+        /* compare with after_state_ch,
+         * os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S */
+        DEFINE_WAIT(wait);
+
+        /* we wait here
+         *    as long as the device is suspended
+         *    until the bitmap is no longer on the fly during connection
+         *    handshake as long as we would exeed the max_buffer limit.
+         *
+         * to avoid races with the reconnect code,
+         * we need to atomic_inc within the spinlock. */
+
+        spin_lock_irq(&mdev->req_lock);
+        while (!__inc_ap_bio_cond(mdev)) {
+                prepare_to_wait(&mdev->misc_wait, &wait, TASK_UNINTERRUPTIBLE);
+                spin_unlock_irq(&mdev->req_lock);
+                schedule();
+                finish_wait(&mdev->misc_wait, &wait);
+                spin_lock_irq(&mdev->req_lock);
+        }
+        atomic_add(one_or_two, &mdev->ap_bio_cnt);
+        spin_unlock_irq(&mdev->req_lock);
+}
+
+static inline void dec_ap_bio(struct drbd_conf *mdev)
+{
+        int mxb = drbd_get_max_buffers(mdev);
+        int ap_bio = atomic_dec_return(&mdev->ap_bio_cnt);
+
+        D_ASSERT(ap_bio >= 0);
+        /* this currently does wake_up for every dec_ap_bio!
+         * maybe rather introduce some type of hysteresis?
+         * e.g. (ap_bio == mxb/2 || ap_bio == 0) ? */
+        if (ap_bio < mxb)
+                wake_up(&mdev->misc_wait);
+        if (ap_bio == 0 && test_bit(BITMAP_IO, &mdev->flags)) {
+                if (!test_and_set_bit(BITMAP_IO_QUEUED, &mdev->flags))
+                        drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
+        }
+}
+
+static inline void drbd_set_ed_uuid(struct drbd_conf *mdev, u64 val)
+{
+        mdev->ed_uuid = val;
+}
+
+static inline int seq_cmp(u32 a, u32 b)
+{
+        /* we assume wrap around at 32bit.
+         * for wrap around at 24bit (old atomic_t),
+         * we'd have to
+         *  a <<= 8; b <<= 8;
+         */
+        return (s32)(a) - (s32)(b);
+}
+#define seq_lt(a, b) (seq_cmp((a), (b)) < 0)
+#define seq_gt(a, b) (seq_cmp((a), (b)) > 0)
+#define seq_ge(a, b) (seq_cmp((a), (b)) >= 0)
+#define seq_le(a, b) (seq_cmp((a), (b)) <= 0)
+/* CAUTION: please no side effects in arguments! */
+#define seq_max(a, b) ((u32)(seq_gt((a), (b)) ? (a) : (b)))
+
+static inline void update_peer_seq(struct drbd_conf *mdev, unsigned int new_seq)
+{
+        unsigned int m;
+        spin_lock(&mdev->peer_seq_lock);
+        m = seq_max(mdev->peer_seq, new_seq);
+        mdev->peer_seq = m;
+        spin_unlock(&mdev->peer_seq_lock);
+        if (m == new_seq)
+                wake_up(&mdev->seq_wait);
+}
+
+static inline void drbd_update_congested(struct drbd_conf *mdev)
+{
+        struct sock *sk = mdev->data.socket->sk;
+        if (sk->sk_wmem_queued > sk->sk_sndbuf * 4 / 5)
+                set_bit(NET_CONGESTED, &mdev->flags);
+}
+
+static inline int drbd_queue_order_type(struct drbd_conf *mdev)
+{
+        /* sorry, we currently have no working implementation
+         * of distributed TCQ stuff */
+#ifndef QUEUE_ORDERED_NONE
+#define QUEUE_ORDERED_NONE 0
+#endif
+        return QUEUE_ORDERED_NONE;
+}
+
+static inline void drbd_blk_run_queue(struct request_queue *q)
+{
+        if (q && q->unplug_fn)
+                q->unplug_fn(q);
+}
+
+static inline void drbd_kick_lo(struct drbd_conf *mdev)
+{
+        if (get_ldev(mdev)) {
+                drbd_blk_run_queue(bdev_get_queue(mdev->ldev->backing_bdev));
+                put_ldev(mdev);
+        }
+}
+
+static inline void drbd_md_flush(struct drbd_conf *mdev)
+{
+        int r;
+
+        if (test_bit(MD_NO_BARRIER, &mdev->flags))
+                return;
+
+        r = blkdev_issue_flush(mdev->ldev->md_bdev, NULL);
+        if (r) {
+                set_bit(MD_NO_BARRIER, &mdev->flags);
+                dev_err(DEV, "meta data flush failed with status %d, disabling md-flushes\n", r);
+        }
+}
+
+#endif
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
new file mode 100644
index 000000000000..edf0b8031e69
--- /dev/null
+++ b/drivers/block/drbd/drbd_main.c
@@ -0,0 +1,3735 @@
+/*
+   drbd.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   Thanks to Carter Burden, Bart Grantham and Gennadiy Nerubayev
+   from Logicworks, Inc. for making SDP replication support possible.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <asm/uaccess.h>
+#include <asm/types.h>
+#include <net/sock.h>
+#include <linux/ctype.h>
+#include <linux/smp_lock.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/reboot.h>
+#include <linux/notifier.h>
+#include <linux/kthread.h>
+
+#define __KERNEL_SYSCALLS__
+#include <linux/unistd.h>
+#include <linux/vmalloc.h>
+
+#include <linux/drbd_limits.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h" /* only for _req_mod in tl_release and tl_clear */
+
+#include "drbd_vli.h"
+
+struct after_state_chg_work {
+        struct drbd_work w;
+        union drbd_state os;
+        union drbd_state ns;
+        enum chg_state_flags flags;
+        struct completion *done;
+};
+
+int drbdd_init(struct drbd_thread *);
+int drbd_worker(struct drbd_thread *);
+int drbd_asender(struct drbd_thread *);
+
+int drbd_init(void);
+static int drbd_open(struct block_device *bdev, fmode_t mode);
+static int drbd_release(struct gendisk *gd, fmode_t mode);
+static int w_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+                           union drbd_state ns, enum chg_state_flags flags);
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void md_sync_timer_fn(unsigned long data);
+static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+
+DEFINE_TRACE(drbd_unplug);
+DEFINE_TRACE(drbd_uuid);
+DEFINE_TRACE(drbd_ee);
+DEFINE_TRACE(drbd_packet);
+DEFINE_TRACE(drbd_md_io);
+DEFINE_TRACE(drbd_epoch);
+DEFINE_TRACE(drbd_netlink);
+DEFINE_TRACE(drbd_actlog);
+DEFINE_TRACE(drbd_bio);
+DEFINE_TRACE(_drbd_resync);
+DEFINE_TRACE(drbd_req);
+
+MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
+              "Lars Ellenberg <lars@linbit.com>");
+MODULE_DESCRIPTION("drbd - Distributed Replicated Block Device v" REL_VERSION);
+MODULE_VERSION(REL_VERSION);
+MODULE_LICENSE("GPL");
+MODULE_PARM_DESC(minor_count, "Maximum number of drbd devices (1-255)");
+MODULE_ALIAS_BLOCKDEV_MAJOR(DRBD_MAJOR);
+
+#include <linux/moduleparam.h>
+/* allow_open_on_secondary */
+MODULE_PARM_DESC(allow_oos, "DONT USE!");
+/* thanks to these macros, if compiled into the kernel (not-module),
+ * this becomes the boot parameter drbd.minor_count */
+module_param(minor_count, uint, 0444);
+module_param(disable_sendpage, bool, 0644);
+module_param(allow_oos, bool, 0);
+module_param(cn_idx, uint, 0444);
+module_param(proc_details, int, 0644);
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+int enable_faults;
+int fault_rate;
+static int fault_count;
+int fault_devs;
+/* bitmap of enabled faults */
+module_param(enable_faults, int, 0664);
+/* fault rate % value - applies to all enabled faults */
+module_param(fault_rate, int, 0664);
+/* count of faults inserted */
+module_param(fault_count, int, 0664);
+/* bitmap of devices to insert faults on */
+module_param(fault_devs, int, 0644);
+#endif
+
+/* module parameter, defined */
+unsigned int minor_count = 32;
+int disable_sendpage;
+int allow_oos;
+unsigned int cn_idx = CN_IDX_DRBD;
+int proc_details;       /* Detail level in proc drbd*/
+
+/* Module parameter for setting the user mode helper program
+ * to run. Default is /sbin/drbdadm */
+char usermode_helper[80] = "/sbin/drbdadm";
+
+module_param_string(usermode_helper, usermode_helper, sizeof(usermode_helper), 0644);
+
+/* in 2.6.x, our device mapping and config info contains our virtual gendisks
+ * as member "struct gendisk *vdisk;"
+ */
+struct drbd_conf **minor_table;
+
+struct kmem_cache *drbd_request_cache;
+struct kmem_cache *drbd_ee_cache;       /* epoch entries */
+struct kmem_cache *drbd_bm_ext_cache;   /* bitmap extents */
+struct kmem_cache *drbd_al_ext_cache;   /* activity log extents */
+mempool_t *drbd_request_mempool;
+mempool_t *drbd_ee_mempool;
+
+/* I do not use a standard mempool, because:
+   1) I want to hand out the pre-allocated objects first.
+   2) I want to be able to interrupt sleeping allocation with a signal.
+   Note: This is a single linked list, the next pointer is the private
+         member of struct page.
+ */
+struct page *drbd_pp_pool;
+spinlock_t   drbd_pp_lock;
+int          drbd_pp_vacant;
+wait_queue_head_t drbd_pp_wait;
+
+DEFINE_RATELIMIT_STATE(drbd_ratelimit_state, 5 * HZ, 5);
+
+static struct block_device_operations drbd_ops = {
+        .owner =   THIS_MODULE,
+        .open =    drbd_open,
+        .release = drbd_release,
+};
+
+#define ARRY_SIZE(A) (sizeof(A)/sizeof(A[0]))
+
+#ifdef __CHECKER__
+/* When checking with sparse, and this is an inline function, sparse will
+   give tons of false positives. When this is a real functions sparse works.
+ */
+int _get_ldev_if_state(struct drbd_conf *mdev, enum drbd_disk_state mins)
+{
+        int io_allowed;
+
+        atomic_inc(&mdev->local_cnt);
+        io_allowed = (mdev->state.disk >= mins);
+        if (!io_allowed) {
+                if (atomic_dec_and_test(&mdev->local_cnt))
+                        wake_up(&mdev->misc_wait);
+        }
+        return io_allowed;
+}
+
+#endif
+
+/**
+ * DOC: The transfer log
+ *
+ * The transfer log is a single linked list of &struct drbd_tl_epoch objects.
+ * mdev->newest_tle points to the head, mdev->oldest_tle points to the tail
+ * of the list. There is always at least one &struct drbd_tl_epoch object.
+ *
+ * Each &struct drbd_tl_epoch has a circular double linked list of requests
+ * attached.
+ */
+static int tl_init(struct drbd_conf *mdev)
+{
+        struct drbd_tl_epoch *b;
+
+        /* during device minor initialization, we may well use GFP_KERNEL */
+        b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_KERNEL);
+        if (!b)
+                return 0;
+        INIT_LIST_HEAD(&b->requests);
+        INIT_LIST_HEAD(&b->w.list);
+        b->next = NULL;
+        b->br_number = 4711;
+        b->n_req = 0;
+        b->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+
+        mdev->oldest_tle = b;
+        mdev->newest_tle = b;
+        INIT_LIST_HEAD(&mdev->out_of_sequence_requests);
+
+        mdev->tl_hash = NULL;
+        mdev->tl_hash_s = 0;
+
+        return 1;
+}
+
+static void tl_cleanup(struct drbd_conf *mdev)
+{
+        D_ASSERT(mdev->oldest_tle == mdev->newest_tle);
+        D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+        kfree(mdev->oldest_tle);
+        mdev->oldest_tle = NULL;
+        kfree(mdev->unused_spare_tle);
+        mdev->unused_spare_tle = NULL;
+        kfree(mdev->tl_hash);
+        mdev->tl_hash = NULL;
+        mdev->tl_hash_s = 0;
+}
+
+/**
+ * _tl_add_barrier() - Adds a barrier to the transfer log
+ * @mdev:       DRBD device.
+ * @new:        Barrier to be added before the current head of the TL.
+ *
+ * The caller must hold the req_lock.
+ */
+void _tl_add_barrier(struct drbd_conf *mdev, struct drbd_tl_epoch *new)
+{
+        struct drbd_tl_epoch *newest_before;
+
+        INIT_LIST_HEAD(&new->requests);
+        INIT_LIST_HEAD(&new->w.list);
+        new->w.cb = NULL; /* if this is != NULL, we need to dec_ap_pending in tl_clear */
+        new->next = NULL;
+        new->n_req = 0;
+
+        newest_before = mdev->newest_tle;
+        /* never send a barrier number == 0, because that is special-cased
+         * when using TCQ for our write ordering code */
+        new->br_number = (newest_before->br_number+1) ?: 1;
+        if (mdev->newest_tle != new) {
+                mdev->newest_tle->next = new;
+                mdev->newest_tle = new;
+        }
+}
+
+/**
+ * tl_release() - Free or recycle the oldest &struct drbd_tl_epoch object of the TL
+ * @mdev:       DRBD device.
+ * @barrier_nr: Expected identifier of the DRBD write barrier packet.
+ * @set_size:   Expected number of requests before that barrier.
+ *
+ * In case the passed barrier_nr or set_size does not match the oldest
+ * &struct drbd_tl_epoch objects this function will cause a termination
+ * of the connection.
+ */
+void tl_release(struct drbd_conf *mdev, unsigned int barrier_nr,
+                       unsigned int set_size)
+{
+        struct drbd_tl_epoch *b, *nob; /* next old barrier */
+        struct list_head *le, *tle;
+        struct drbd_request *r;
+
+        spin_lock_irq(&mdev->req_lock);
+
+        b = mdev->oldest_tle;
+
+        /* first some paranoia code */
+        if (b == NULL) {
+                dev_err(DEV, "BAD! BarrierAck #%u received, but no epoch in tl!?\n",
+                        barrier_nr);
+                goto bail;
+        }
+        if (b->br_number != barrier_nr) {
+                dev_err(DEV, "BAD! BarrierAck #%u received, expected #%u!\n",
+                        barrier_nr, b->br_number);
+                goto bail;
+        }
+        if (b->n_req != set_size) {
+                dev_err(DEV, "BAD! BarrierAck #%u received with n_req=%u, expected n_req=%u!\n",
+                        barrier_nr, set_size, b->n_req);
+                goto bail;
+        }
+
+        /* Clean up list of requests processed during current epoch */
+        list_for_each_safe(le, tle, &b->requests) {
+                r = list_entry(le, struct drbd_request, tl_requests);
+                _req_mod(r, barrier_acked);
+        }
+        /* There could be requests on the list waiting for completion
+           of the write to the local disk. To avoid corruptions of
+           slab's data structures we have to remove the lists head.
+
+           Also there could have been a barrier ack out of sequence, overtaking
+           the write acks - which would be a bug and violating write ordering.
+           To not deadlock in case we lose connection while such requests are
+           still pending, we need some way to find them for the
+           _req_mode(connection_lost_while_pending).
+
+           These have been list_move'd to the out_of_sequence_requests list in
+           _req_mod(, barrier_acked) above.
+           */
+        list_del_init(&b->requests);
+
+        nob = b->next;
+        if (test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+                _tl_add_barrier(mdev, b);
+                if (nob)
+                        mdev->oldest_tle = nob;
+                /* if nob == NULL b was the only barrier, and becomes the new
+                   barrier. Therefore mdev->oldest_tle points already to b */
+        } else {
+                D_ASSERT(nob != NULL);
+                mdev->oldest_tle = nob;
+                kfree(b);
+        }
+
+        spin_unlock_irq(&mdev->req_lock);
+        dec_ap_pending(mdev);
+
+        return;
+
+bail:
+        spin_unlock_irq(&mdev->req_lock);
+        drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+}
+
+
+/**
+ * tl_clear() - Clears all requests and &struct drbd_tl_epoch objects out of the TL
+ * @mdev:       DRBD device.
+ *
+ * This is called after the connection to the peer was lost. The storage covered
+ * by the requests on the transfer gets marked as our of sync. Called from the
+ * receiver thread and the worker thread.
+ */
+void tl_clear(struct drbd_conf *mdev)
+{
+        struct drbd_tl_epoch *b, *tmp;
+        struct list_head *le, *tle;
+        struct drbd_request *r;
+        int new_initial_bnr = net_random();
+
+        spin_lock_irq(&mdev->req_lock);
+
+        b = mdev->oldest_tle;
+        while (b) {
+                list_for_each_safe(le, tle, &b->requests) {
+                        r = list_entry(le, struct drbd_request, tl_requests);
+                        /* It would be nice to complete outside of spinlock.
+                         * But this is easier for now. */
+                        _req_mod(r, connection_lost_while_pending);
+                }
+                tmp = b->next;
+
+                /* there could still be requests on that ring list,
+                 * in case local io is still pending */
+                list_del(&b->requests);
+
+                /* dec_ap_pending corresponding to queue_barrier.
+                 * the newest barrier may not have been queued yet,
+                 * in which case w.cb is still NULL. */
+                if (b->w.cb != NULL)
+                        dec_ap_pending(mdev);
+
+                if (b == mdev->newest_tle) {
+                        /* recycle, but reinit! */
+                        D_ASSERT(tmp == NULL);
+                        INIT_LIST_HEAD(&b->requests);
+                        INIT_LIST_HEAD(&b->w.list);
+                        b->w.cb = NULL;
+                        b->br_number = new_initial_bnr;
+                        b->n_req = 0;
+
+                        mdev->oldest_tle = b;
+                        break;
+                }
+                kfree(b);
+                b = tmp;
+        }
+
+        /* we expect this list to be empty. */
+        D_ASSERT(list_empty(&mdev->out_of_sequence_requests));
+
+        /* but just in case, clean it up anyways! */
+        list_for_each_safe(le, tle, &mdev->out_of_sequence_requests) {
+                r = list_entry(le, struct drbd_request, tl_requests);
+                /* It would be nice to complete outside of spinlock.
+                 * But this is easier for now. */
+                _req_mod(r, connection_lost_while_pending);
+        }
+
+        /* ensure bit indicating barrier is required is clear */
+        clear_bit(CREATE_BARRIER, &mdev->flags);
+
+        spin_unlock_irq(&mdev->req_lock);
+}
+
+/**
+ * cl_wide_st_chg() - TRUE if the state change is a cluster wide one
+ * @mdev:       DRBD device.
+ * @os:         old (current) state.
+ * @ns:         new (wanted) state.
+ */
+static int cl_wide_st_chg(struct drbd_conf *mdev,
+                          union drbd_state os, union drbd_state ns)
+{
+        return (os.conn >= C_CONNECTED && ns.conn >= C_CONNECTED &&
+                 ((os.role != R_PRIMARY && ns.role == R_PRIMARY) ||
+                  (os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+                  (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S) ||
+                  (os.disk != D_DISKLESS && ns.disk == D_DISKLESS))) ||
+                (os.conn >= C_CONNECTED && ns.conn == C_DISCONNECTING) ||
+                (os.conn == C_CONNECTED && ns.conn == C_VERIFY_S);
+}
+
+int drbd_change_state(struct drbd_conf *mdev, enum chg_state_flags f,
+                      union drbd_state mask, union drbd_state val)
+{
+        unsigned long flags;
+        union drbd_state os, ns;
+        int rv;
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        os = mdev->state;
+        ns.i = (os.i & ~mask.i) | val.i;
+        rv = _drbd_set_state(mdev, ns, f, NULL);
+        ns = mdev->state;
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        return rv;
+}
+
+/**
+ * drbd_force_state() - Impose a change which happens outside our control on our state
+ * @mdev:       DRBD device.
+ * @mask:       mask of state bits to change.
+ * @val:        value of new state bits.
+ */
+void drbd_force_state(struct drbd_conf *mdev,
+        union drbd_state mask, union drbd_state val)
+{
+        drbd_change_state(mdev, CS_HARD, mask, val);
+}
+
+static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns);
+static int is_valid_state_transition(struct drbd_conf *,
+                                     union drbd_state, union drbd_state);
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+                                       union drbd_state ns, int *warn_sync_abort);
+int drbd_send_state_req(struct drbd_conf *,
+                        union drbd_state, union drbd_state);
+
+static enum drbd_state_ret_codes _req_st_cond(struct drbd_conf *mdev,
+                                    union drbd_state mask, union drbd_state val)
+{
+        union drbd_state os, ns;
+        unsigned long flags;
+        int rv;
+
+        if (test_and_clear_bit(CL_ST_CHG_SUCCESS, &mdev->flags))
+                return SS_CW_SUCCESS;
+
+        if (test_and_clear_bit(CL_ST_CHG_FAIL, &mdev->flags))
+                return SS_CW_FAILED_BY_PEER;
+
+        rv = 0;
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        os = mdev->state;
+        ns.i = (os.i & ~mask.i) | val.i;
+        ns = sanitize_state(mdev, os, ns, NULL);
+
+        if (!cl_wide_st_chg(mdev, os, ns))
+                rv = SS_CW_NO_NEED;
+        if (!rv) {
+                rv = is_valid_state(mdev, ns);
+                if (rv == SS_SUCCESS) {
+                        rv = is_valid_state_transition(mdev, ns, os);
+                        if (rv == SS_SUCCESS)
+                                rv = 0; /* cont waiting, otherwise fail. */
+                }
+        }
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        return rv;
+}
+
+/**
+ * drbd_req_state() - Perform an eventually cluster wide state change
+ * @mdev:       DRBD device.
+ * @mask:       mask of state bits to change.
+ * @val:        value of new state bits.
+ * @f:          flags
+ *
+ * Should not be called directly, use drbd_request_state() or
+ * _drbd_request_state().
+ */
+static int drbd_req_state(struct drbd_conf *mdev,
+                          union drbd_state mask, union drbd_state val,
+                          enum chg_state_flags f)
+{
+        struct completion done;
+        unsigned long flags;
+        union drbd_state os, ns;
+        int rv;
+
+        init_completion(&done);
+
+        if (f & CS_SERIALIZE)
+                mutex_lock(&mdev->state_mutex);
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        os = mdev->state;
+        ns.i = (os.i & ~mask.i) | val.i;
+        ns = sanitize_state(mdev, os, ns, NULL);
+
+        if (cl_wide_st_chg(mdev, os, ns)) {
+                rv = is_valid_state(mdev, ns);
+                if (rv == SS_SUCCESS)
+                        rv = is_valid_state_transition(mdev, ns, os);
+                spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+                if (rv < SS_SUCCESS) {
+                        if (f & CS_VERBOSE)
+                                print_st_err(mdev, os, ns, rv);
+                        goto abort;
+                }
+
+                drbd_state_lock(mdev);
+                if (!drbd_send_state_req(mdev, mask, val)) {
+                        drbd_state_unlock(mdev);
+                        rv = SS_CW_FAILED_BY_PEER;
+                        if (f & CS_VERBOSE)
+                                print_st_err(mdev, os, ns, rv);
+                        goto abort;
+                }
+
+                wait_event(mdev->state_wait,
+                        (rv = _req_st_cond(mdev, mask, val)));
+
+                if (rv < SS_SUCCESS) {
+                        drbd_state_unlock(mdev);
+                        if (f & CS_VERBOSE)
+                                print_st_err(mdev, os, ns, rv);
+                        goto abort;
+                }
+                spin_lock_irqsave(&mdev->req_lock, flags);
+                os = mdev->state;
+                ns.i = (os.i & ~mask.i) | val.i;
+                rv = _drbd_set_state(mdev, ns, f, &done);
+                drbd_state_unlock(mdev);
+        } else {
+                rv = _drbd_set_state(mdev, ns, f, &done);
+        }
+
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        if (f & CS_WAIT_COMPLETE && rv == SS_SUCCESS) {
+                D_ASSERT(current != mdev->worker.task);
+                wait_for_completion(&done);
+        }
+
+abort:
+        if (f & CS_SERIALIZE)
+                mutex_unlock(&mdev->state_mutex);
+
+        return rv;
+}
+
+/**
+ * _drbd_request_state() - Request a state change (with flags)
+ * @mdev:       DRBD device.
+ * @mask:       mask of state bits to change.
+ * @val:        value of new state bits.
+ * @f:          flags
+ *
+ * Cousin of drbd_request_state(), useful with the CS_WAIT_COMPLETE
+ * flag, or when logging of failed state change requests is not desired.
+ */
+int _drbd_request_state(struct drbd_conf *mdev, union drbd_state mask,
+                        union drbd_state val,   enum chg_state_flags f)
+{
+        int rv;
+
+        wait_event(mdev->state_wait,
+                   (rv = drbd_req_state(mdev, mask, val, f)) != SS_IN_TRANSIENT_STATE);
+
+        return rv;
+}
+
+static void print_st(struct drbd_conf *mdev, char *name, union drbd_state ns)
+{
+        dev_err(DEV, " %s = { cs:%s ro:%s/%s ds:%s/%s %c%c%c%c }\n",
+            name,
+            drbd_conn_str(ns.conn),
+            drbd_role_str(ns.role),
+            drbd_role_str(ns.peer),
+            drbd_disk_str(ns.disk),
+            drbd_disk_str(ns.pdsk),
+            ns.susp ? 's' : 'r',
+            ns.aftr_isp ? 'a' : '-',
+            ns.peer_isp ? 'p' : '-',
+            ns.user_isp ? 'u' : '-'
+            );
+}
+
+void print_st_err(struct drbd_conf *mdev,
+        union drbd_state os, union drbd_state ns, int err)
+{
+        if (err == SS_IN_TRANSIENT_STATE)
+                return;
+        dev_err(DEV, "State change failed: %s\n", drbd_set_st_err_str(err));
+        print_st(mdev, " state", os);
+        print_st(mdev, "wanted", ns);
+}
+
+
+#define drbd_peer_str drbd_role_str
+#define drbd_pdsk_str drbd_disk_str
+
+#define drbd_susp_str(A)     ((A) ? "1" : "0")
+#define drbd_aftr_isp_str(A) ((A) ? "1" : "0")
+#define drbd_peer_isp_str(A) ((A) ? "1" : "0")
+#define drbd_user_isp_str(A) ((A) ? "1" : "0")
+
+#define PSC(A) \
+        ({ if (ns.A != os.A) { \
+                pbp += sprintf(pbp, #A "( %s -> %s ) ", \
+                              drbd_##A##_str(os.A), \
+                              drbd_##A##_str(ns.A)); \
+        } })
+
+/**
+ * is_valid_state() - Returns an SS_ error code if ns is not valid
+ * @mdev:       DRBD device.
+ * @ns:         State to consider.
+ */
+static int is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
+{
+        /* See drbd_state_sw_errors in drbd_strings.c */
+
+        enum drbd_fencing_p fp;
+        int rv = SS_SUCCESS;
+
+        fp = FP_DONT_CARE;
+        if (get_ldev(mdev)) {
+                fp = mdev->ldev->dc.fencing;
+                put_ldev(mdev);
+        }
+
+        if (get_net_conf(mdev)) {
+                if (!mdev->net_conf->two_primaries &&
+                    ns.role == R_PRIMARY && ns.peer == R_PRIMARY)
+                        rv = SS_TWO_PRIMARIES;
+                put_net_conf(mdev);
+        }
+
+        if (rv <= 0)
+                /* already found a reason to abort */;
+        else if (ns.role == R_SECONDARY && mdev->open_cnt)
+                rv = SS_DEVICE_IN_USE;
+
+        else if (ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.disk < D_UP_TO_DATE)
+                rv = SS_NO_UP_TO_DATE_DISK;
+
+        else if (fp >= FP_RESOURCE &&
+                 ns.role == R_PRIMARY && ns.conn < C_CONNECTED && ns.pdsk >= D_UNKNOWN)
+                rv = SS_PRIMARY_NOP;
+
+        else if (ns.role == R_PRIMARY && ns.disk <= D_INCONSISTENT && ns.pdsk <= D_INCONSISTENT)
+                rv = SS_NO_UP_TO_DATE_DISK;
+
+        else if (ns.conn > C_CONNECTED && ns.disk < D_INCONSISTENT)
+                rv = SS_NO_LOCAL_DISK;
+
+        else if (ns.conn > C_CONNECTED && ns.pdsk < D_INCONSISTENT)
+                rv = SS_NO_REMOTE_DISK;
+
+        else if ((ns.conn == C_CONNECTED ||
+                  ns.conn == C_WF_BITMAP_S ||
+                  ns.conn == C_SYNC_SOURCE ||
+                  ns.conn == C_PAUSED_SYNC_S) &&
+                  ns.disk == D_OUTDATED)
+                rv = SS_CONNECTED_OUTDATES;
+
+        else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+                 (mdev->sync_conf.verify_alg[0] == 0))
+                rv = SS_NO_VERIFY_ALG;
+
+        else if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+                  mdev->agreed_pro_version < 88)
+                rv = SS_NOT_SUPPORTED;
+
+        return rv;
+}
+
+/**
+ * is_valid_state_transition() - Returns an SS_ error code if the state transition is not possible
+ * @mdev:       DRBD device.
+ * @ns:         new state.
+ * @os:         old state.
+ */
+static int is_valid_state_transition(struct drbd_conf *mdev,
+                                     union drbd_state ns, union drbd_state os)
+{
+        int rv = SS_SUCCESS;
+
+        if ((ns.conn == C_STARTING_SYNC_T || ns.conn == C_STARTING_SYNC_S) &&
+            os.conn > C_CONNECTED)
+                rv = SS_RESYNC_RUNNING;
+
+        if (ns.conn == C_DISCONNECTING && os.conn == C_STANDALONE)
+                rv = SS_ALREADY_STANDALONE;
+
+        if (ns.disk > D_ATTACHING && os.disk == D_DISKLESS)
+                rv = SS_IS_DISKLESS;
+
+        if (ns.conn == C_WF_CONNECTION && os.conn < C_UNCONNECTED)
+                rv = SS_NO_NET_CONFIG;
+
+        if (ns.disk == D_OUTDATED && os.disk < D_OUTDATED && os.disk != D_ATTACHING)
+                rv = SS_LOWER_THAN_OUTDATED;
+
+        if (ns.conn == C_DISCONNECTING && os.conn == C_UNCONNECTED)
+                rv = SS_IN_TRANSIENT_STATE;
+
+        if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
+                rv = SS_IN_TRANSIENT_STATE;
+
+        if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
+                rv = SS_NEED_CONNECTION;
+
+        if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) &&
+            ns.conn != os.conn && os.conn > C_CONNECTED)
+                rv = SS_RESYNC_RUNNING;
+
+        if ((ns.conn == C_STARTING_SYNC_S || ns.conn == C_STARTING_SYNC_T) &&
+            os.conn < C_CONNECTED)
+                rv = SS_NEED_CONNECTION;
+
+        return rv;
+}
+
+/**
+ * sanitize_state() - Resolves implicitly necessary additional changes to a state transition
+ * @mdev:       DRBD device.
+ * @os:         old state.
+ * @ns:         new state.
+ * @warn_sync_abort:
+ *
+ * When we loose connection, we have to set the state of the peers disk (pdsk)
+ * to D_UNKNOWN. This rule and many more along those lines are in this function.
+ */
+static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state os,
+                                       union drbd_state ns, int *warn_sync_abort)
+{
+        enum drbd_fencing_p fp;
+
+        fp = FP_DONT_CARE;
+        if (get_ldev(mdev)) {
+                fp = mdev->ldev->dc.fencing;
+                put_ldev(mdev);
+        }
+
+        /* Disallow Network errors to configure a device's network part */
+        if ((ns.conn >= C_TIMEOUT && ns.conn <= C_TEAR_DOWN) &&
+            os.conn <= C_DISCONNECTING)
+                ns.conn = os.conn;
+
+        /* After a network error (+C_TEAR_DOWN) only C_UNCONNECTED or C_DISCONNECTING can follow */
+        if (os.conn >= C_TIMEOUT && os.conn <= C_TEAR_DOWN &&
+            ns.conn != C_UNCONNECTED && ns.conn != C_DISCONNECTING)
+                ns.conn = os.conn;
+
+        /* After C_DISCONNECTING only C_STANDALONE may follow */
+        if (os.conn == C_DISCONNECTING && ns.conn != C_STANDALONE)
+                ns.conn = os.conn;
+
+        if (ns.conn < C_CONNECTED) {
+                ns.peer_isp = 0;
+                ns.peer = R_UNKNOWN;
+                if (ns.pdsk > D_UNKNOWN || ns.pdsk < D_INCONSISTENT)
+                        ns.pdsk = D_UNKNOWN;
+        }
+
+        /* Clear the aftr_isp when becoming unconfigured */
+        if (ns.conn == C_STANDALONE && ns.disk == D_DISKLESS && ns.role == R_SECONDARY)
+                ns.aftr_isp = 0;
+
+        if (ns.conn <= C_DISCONNECTING && ns.disk == D_DISKLESS)
+                ns.pdsk = D_UNKNOWN;
+
+        /* Abort resync if a disk fails/detaches */
+        if (os.conn > C_CONNECTED && ns.conn > C_CONNECTED &&
+            (ns.disk <= D_FAILED || ns.pdsk <= D_FAILED)) {
+                if (warn_sync_abort)
+                        *warn_sync_abort = 1;
+                ns.conn = C_CONNECTED;
+        }
+
+        if (ns.conn >= C_CONNECTED &&
+            ((ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED) ||
+             (ns.disk == D_NEGOTIATING && ns.conn == C_WF_BITMAP_T))) {
+                switch (ns.conn) {
+                case C_WF_BITMAP_T:
+                case C_PAUSED_SYNC_T:
+                        ns.disk = D_OUTDATED;
+                        break;
+                case C_CONNECTED:
+                case C_WF_BITMAP_S:
+                case C_SYNC_SOURCE:
+                case C_PAUSED_SYNC_S:
+                        ns.disk = D_UP_TO_DATE;
+                        break;
+                case C_SYNC_TARGET:
+                        ns.disk = D_INCONSISTENT;
+                        dev_warn(DEV, "Implicitly set disk state Inconsistent!\n");
+                        break;
+                }
+                if (os.disk == D_OUTDATED && ns.disk == D_UP_TO_DATE)
+                        dev_warn(DEV, "Implicitly set disk from Outdated to UpToDate\n");
+        }
+
+        if (ns.conn >= C_CONNECTED &&
+            (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)) {
+                switch (ns.conn) {
+                case C_CONNECTED:
+                case C_WF_BITMAP_T:
+                case C_PAUSED_SYNC_T:
+                case C_SYNC_TARGET:
+                        ns.pdsk = D_UP_TO_DATE;
+                        break;
+                case C_WF_BITMAP_S:
+                case C_PAUSED_SYNC_S:
+                        ns.pdsk = D_OUTDATED;
+                        break;
+                case C_SYNC_SOURCE:
+                        ns.pdsk = D_INCONSISTENT;
+                        dev_warn(DEV, "Implicitly set pdsk Inconsistent!\n");
+                        break;
+                }
+                if (os.pdsk == D_OUTDATED && ns.pdsk == D_UP_TO_DATE)
+                        dev_warn(DEV, "Implicitly set pdsk from Outdated to UpToDate\n");
+        }
+
+        /* Connection breaks down before we finished "Negotiating" */
+        if (ns.conn < C_CONNECTED && ns.disk == D_NEGOTIATING &&
+            get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                if (mdev->ed_uuid == mdev->ldev->md.uuid[UI_CURRENT]) {
+                        ns.disk = mdev->new_state_tmp.disk;
+                        ns.pdsk = mdev->new_state_tmp.pdsk;
+                } else {
+                        dev_alert(DEV, "Connection lost while negotiating, no data!\n");
+                        ns.disk = D_DISKLESS;
+                        ns.pdsk = D_UNKNOWN;
+                }
+                put_ldev(mdev);
+        }
+
+        if (fp == FP_STONITH &&
+            (ns.role == R_PRIMARY &&
+             ns.conn < C_CONNECTED &&
+             ns.pdsk > D_OUTDATED))
+                        ns.susp = 1;
+
+        if (ns.aftr_isp || ns.peer_isp || ns.user_isp) {
+                if (ns.conn == C_SYNC_SOURCE)
+                        ns.conn = C_PAUSED_SYNC_S;
+                if (ns.conn == C_SYNC_TARGET)
+                        ns.conn = C_PAUSED_SYNC_T;
+        } else {
+                if (ns.conn == C_PAUSED_SYNC_S)
+                        ns.conn = C_SYNC_SOURCE;
+                if (ns.conn == C_PAUSED_SYNC_T)
+                        ns.conn = C_SYNC_TARGET;
+        }
+
+        return ns;
+}
+
+/* helper for __drbd_set_state */
+static void set_ov_position(struct drbd_conf *mdev, enum drbd_conns cs)
+{
+        if (cs == C_VERIFY_T) {
+                /* starting online verify from an arbitrary position
+                 * does not fit well into the existing protocol.
+                 * on C_VERIFY_T, we initialize ov_left and friends
+                 * implicitly in receive_DataRequest once the
+                 * first P_OV_REQUEST is received */
+                mdev->ov_start_sector = ~(sector_t)0;
+        } else {
+                unsigned long bit = BM_SECT_TO_BIT(mdev->ov_start_sector);
+                if (bit >= mdev->rs_total)
+                        mdev->ov_start_sector =
+                                BM_BIT_TO_SECT(mdev->rs_total - 1);
+                mdev->ov_position = mdev->ov_start_sector;
+        }
+}
+
+/**
+ * __drbd_set_state() - Set a new DRBD state
+ * @mdev:       DRBD device.
+ * @ns:         new state.
+ * @flags:      Flags
+ * @done:       Optional completion, that will get completed after the after_state_ch() finished
+ *
+ * Caller needs to hold req_lock, and global_state_lock. Do not call directly.
+ */
+int __drbd_set_state(struct drbd_conf *mdev,
+                    union drbd_state ns, enum chg_state_flags flags,
+                    struct completion *done)
+{
+        union drbd_state os;
+        int rv = SS_SUCCESS;
+        int warn_sync_abort = 0;
+        struct after_state_chg_work *ascw;
+
+        os = mdev->state;
+
+        ns = sanitize_state(mdev, os, ns, &warn_sync_abort);
+
+        if (ns.i == os.i)
+                return SS_NOTHING_TO_DO;
+
+        if (!(flags & CS_HARD)) {
+                /*  pre-state-change checks ; only look at ns  */
+                /* See drbd_state_sw_errors in drbd_strings.c */
+
+                rv = is_valid_state(mdev, ns);
+                if (rv < SS_SUCCESS) {
+                        /* If the old state was illegal as well, then let
+                           this happen...*/
+
+                        if (is_valid_state(mdev, os) == rv) {
+                                dev_err(DEV, "Considering state change from bad state. "
+                                    "Error would be: '%s'\n",
+                                    drbd_set_st_err_str(rv));
+                                print_st(mdev, "old", os);
+                                print_st(mdev, "new", ns);
+                                rv = is_valid_state_transition(mdev, ns, os);
+                        }
+                } else
+                        rv = is_valid_state_transition(mdev, ns, os);
+        }
+
+        if (rv < SS_SUCCESS) {
+                if (flags & CS_VERBOSE)
+                        print_st_err(mdev, os, ns, rv);
+                return rv;
+        }
+
+        if (warn_sync_abort)
+                dev_warn(DEV, "Resync aborted.\n");
+
+        {
+                char *pbp, pb[300];
+                pbp = pb;
+                *pbp = 0;
+                PSC(role);
+                PSC(peer);
+                PSC(conn);
+                PSC(disk);
+                PSC(pdsk);
+                PSC(susp);
+                PSC(aftr_isp);
+                PSC(peer_isp);
+                PSC(user_isp);
+                dev_info(DEV, "%s\n", pb);
+        }
+
+        /* solve the race between becoming unconfigured,
+         * worker doing the cleanup, and
+         * admin reconfiguring us:
+         * on (re)configure, first set CONFIG_PENDING,
+         * then wait for a potentially exiting worker,
+         * start the worker, and schedule one no_op.
+         * then proceed with configuration.
+         */
+        if (ns.disk == D_DISKLESS &&
+            ns.conn == C_STANDALONE &&
+            ns.role == R_SECONDARY &&
+            !test_and_set_bit(CONFIG_PENDING, &mdev->flags))
+                set_bit(DEVICE_DYING, &mdev->flags);
+
+        mdev->state.i = ns.i;
+        wake_up(&mdev->misc_wait);
+        wake_up(&mdev->state_wait);
+
+        /*   post-state-change actions   */
+        if (os.conn >= C_SYNC_SOURCE   && ns.conn <= C_CONNECTED) {
+                set_bit(STOP_SYNC_TIMER, &mdev->flags);
+                mod_timer(&mdev->resync_timer, jiffies);
+        }
+
+        /* aborted verify run. log the last position */
+        if ((os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) &&
+            ns.conn < C_CONNECTED) {
+                mdev->ov_start_sector =
+                        BM_BIT_TO_SECT(mdev->rs_total - mdev->ov_left);
+                dev_info(DEV, "Online Verify reached sector %llu\n",
+                        (unsigned long long)mdev->ov_start_sector);
+        }
+
+        if ((os.conn == C_PAUSED_SYNC_T || os.conn == C_PAUSED_SYNC_S) &&
+            (ns.conn == C_SYNC_TARGET  || ns.conn == C_SYNC_SOURCE)) {
+                dev_info(DEV, "Syncer continues.\n");
+                mdev->rs_paused += (long)jiffies-(long)mdev->rs_mark_time;
+                if (ns.conn == C_SYNC_TARGET) {
+                        if (!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))
+                                mod_timer(&mdev->resync_timer, jiffies);
+                        /* This if (!test_bit) is only needed for the case
+                           that a device that has ceased to used its timer,
+                           i.e. it is already in drbd_resync_finished() gets
+                           paused and resumed. */
+                }
+        }
+
+        if ((os.conn == C_SYNC_TARGET  || os.conn == C_SYNC_SOURCE) &&
+            (ns.conn == C_PAUSED_SYNC_T || ns.conn == C_PAUSED_SYNC_S)) {
+                dev_info(DEV, "Resync suspended\n");
+                mdev->rs_mark_time = jiffies;
+                if (ns.conn == C_PAUSED_SYNC_T)
+                        set_bit(STOP_SYNC_TIMER, &mdev->flags);
+        }
+
+        if (os.conn == C_CONNECTED &&
+            (ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T)) {
+                mdev->ov_position = 0;
+                mdev->rs_total =
+                mdev->rs_mark_left = drbd_bm_bits(mdev);
+                if (mdev->agreed_pro_version >= 90)
+                        set_ov_position(mdev, ns.conn);
+                else
+                        mdev->ov_start_sector = 0;
+                mdev->ov_left = mdev->rs_total
+                              - BM_SECT_TO_BIT(mdev->ov_position);
+                mdev->rs_start     =
+                mdev->rs_mark_time = jiffies;
+                mdev->ov_last_oos_size = 0;
+                mdev->ov_last_oos_start = 0;
+
+                if (ns.conn == C_VERIFY_S) {
+                        dev_info(DEV, "Starting Online Verify from sector %llu\n",
+                                        (unsigned long long)mdev->ov_position);
+                        mod_timer(&mdev->resync_timer, jiffies);
+                }
+        }
+
+        if (get_ldev(mdev)) {
+                u32 mdf = mdev->ldev->md.flags & ~(MDF_CONSISTENT|MDF_PRIMARY_IND|
+                                                 MDF_CONNECTED_IND|MDF_WAS_UP_TO_DATE|
+                                                 MDF_PEER_OUT_DATED|MDF_CRASHED_PRIMARY);
+
+                if (test_bit(CRASHED_PRIMARY, &mdev->flags))
+                        mdf |= MDF_CRASHED_PRIMARY;
+                if (mdev->state.role == R_PRIMARY ||
+                    (mdev->state.pdsk < D_INCONSISTENT && mdev->state.peer == R_PRIMARY))
+                        mdf |= MDF_PRIMARY_IND;
+                if (mdev->state.conn > C_WF_REPORT_PARAMS)
+                        mdf |= MDF_CONNECTED_IND;
+                if (mdev->state.disk > D_INCONSISTENT)
+                        mdf |= MDF_CONSISTENT;
+                if (mdev->state.disk > D_OUTDATED)
+                        mdf |= MDF_WAS_UP_TO_DATE;
+                if (mdev->state.pdsk <= D_OUTDATED && mdev->state.pdsk >= D_INCONSISTENT)
+                        mdf |= MDF_PEER_OUT_DATED;
+                if (mdf != mdev->ldev->md.flags) {
+                        mdev->ldev->md.flags = mdf;
+                        drbd_md_mark_dirty(mdev);
+                }
+                if (os.disk < D_CONSISTENT && ns.disk >= D_CONSISTENT)
+                        drbd_set_ed_uuid(mdev, mdev->ldev->md.uuid[UI_CURRENT]);
+                put_ldev(mdev);
+        }
+
+        /* Peer was forced D_UP_TO_DATE & R_PRIMARY, consider to resync */
+        if (os.disk == D_INCONSISTENT && os.pdsk == D_INCONSISTENT &&
+            os.peer == R_SECONDARY && ns.peer == R_PRIMARY)
+                set_bit(CONSIDER_RESYNC, &mdev->flags);
+
+        /* Receiver should clean up itself */
+        if (os.conn != C_DISCONNECTING && ns.conn == C_DISCONNECTING)
+                drbd_thread_stop_nowait(&mdev->receiver);
+
+        /* Now the receiver finished cleaning up itself, it should die */
+        if (os.conn != C_STANDALONE && ns.conn == C_STANDALONE)
+                drbd_thread_stop_nowait(&mdev->receiver);
+
+        /* Upon network failure, we need to restart the receiver. */
+        if (os.conn > C_TEAR_DOWN &&
+            ns.conn <= C_TEAR_DOWN && ns.conn >= C_TIMEOUT)
+                drbd_thread_restart_nowait(&mdev->receiver);
+
+        ascw = kmalloc(sizeof(*ascw), GFP_ATOMIC);
+        if (ascw) {
+                ascw->os = os;
+                ascw->ns = ns;
+                ascw->flags = flags;
+                ascw->w.cb = w_after_state_ch;
+                ascw->done = done;
+                drbd_queue_work(&mdev->data.work, &ascw->w);
+        } else {
+                dev_warn(DEV, "Could not kmalloc an ascw\n");
+        }
+
+        return rv;
+}
+
+static int w_after_state_ch(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct after_state_chg_work *ascw =
+                container_of(w, struct after_state_chg_work, w);
+        after_state_ch(mdev, ascw->os, ascw->ns, ascw->flags);
+        if (ascw->flags & CS_WAIT_COMPLETE) {
+                D_ASSERT(ascw->done != NULL);
+                complete(ascw->done);
+        }
+        kfree(ascw);
+
+        return 1;
+}
+
+static void abw_start_sync(struct drbd_conf *mdev, int rv)
+{
+        if (rv) {
+                dev_err(DEV, "Writing the bitmap failed not starting resync.\n");
+                _drbd_request_state(mdev, NS(conn, C_CONNECTED), CS_VERBOSE);
+                return;
+        }
+
+        switch (mdev->state.conn) {
+        case C_STARTING_SYNC_T:
+                _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+                break;
+        case C_STARTING_SYNC_S:
+                drbd_start_resync(mdev, C_SYNC_SOURCE);
+                break;
+        }
+}
+
+/**
+ * after_state_ch() - Perform after state change actions that may sleep
+ * @mdev:       DRBD device.
+ * @os:         old state.
+ * @ns:         new state.
+ * @flags:      Flags
+ */
+static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
+                           union drbd_state ns, enum chg_state_flags flags)
+{
+        enum drbd_fencing_p fp;
+
+        if (os.conn != C_CONNECTED && ns.conn == C_CONNECTED) {
+                clear_bit(CRASHED_PRIMARY, &mdev->flags);
+                if (mdev->p_uuid)
+                        mdev->p_uuid[UI_FLAGS] &= ~((u64)2);
+        }
+
+        fp = FP_DONT_CARE;
+        if (get_ldev(mdev)) {
+                fp = mdev->ldev->dc.fencing;
+                put_ldev(mdev);
+        }
+
+        /* Inform userspace about the change... */
+        drbd_bcast_state(mdev, ns);
+
+        if (!(os.role == R_PRIMARY && os.disk < D_UP_TO_DATE && os.pdsk < D_UP_TO_DATE) &&
+            (ns.role == R_PRIMARY && ns.disk < D_UP_TO_DATE && ns.pdsk < D_UP_TO_DATE))
+                drbd_khelper(mdev, "pri-on-incon-degr");
+
+        /* Here we have the actions that are performed after a
+           state change. This function might sleep */
+
+        if (fp == FP_STONITH && ns.susp) {
+                /* case1: The outdate peer handler is successful:
+                 * case2: The connection was established again: */
+                if ((os.pdsk > D_OUTDATED  && ns.pdsk <= D_OUTDATED) ||
+                    (os.conn < C_CONNECTED && ns.conn >= C_CONNECTED)) {
+                        tl_clear(mdev);
+                        spin_lock_irq(&mdev->req_lock);
+                        _drbd_set_state(_NS(mdev, susp, 0), CS_VERBOSE, NULL);
+                        spin_unlock_irq(&mdev->req_lock);
+                }
+        }
+        /* Do not change the order of the if above and the two below... */
+        if (os.pdsk == D_DISKLESS && ns.pdsk > D_DISKLESS) {      /* attach on the peer */
+                drbd_send_uuids(mdev);
+                drbd_send_state(mdev);
+        }
+        if (os.conn != C_WF_BITMAP_S && ns.conn == C_WF_BITMAP_S)
+                drbd_queue_bitmap_io(mdev, &drbd_send_bitmap, NULL, "send_bitmap (WFBitMapS)");
+
+        /* Lost contact to peer's copy of the data */
+        if ((os.pdsk >= D_INCONSISTENT &&
+             os.pdsk != D_UNKNOWN &&
+             os.pdsk != D_OUTDATED)
+        &&  (ns.pdsk < D_INCONSISTENT ||
+             ns.pdsk == D_UNKNOWN ||
+             ns.pdsk == D_OUTDATED)) {
+                kfree(mdev->p_uuid);
+                mdev->p_uuid = NULL;
+                if (get_ldev(mdev)) {
+                        if ((ns.role == R_PRIMARY || ns.peer == R_PRIMARY) &&
+                            mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+                                drbd_uuid_new_current(mdev);
+                                drbd_send_uuids(mdev);
+                        }
+                        put_ldev(mdev);
+                }
+        }
+
+        if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
+                if (ns.peer == R_PRIMARY && mdev->ldev->md.uuid[UI_BITMAP] == 0)
+                        drbd_uuid_new_current(mdev);
+
+                /* D_DISKLESS Peer becomes secondary */
+                if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
+                        drbd_al_to_on_disk_bm(mdev);
+                put_ldev(mdev);
+        }
+
+        /* Last part of the attaching process ... */
+        if (ns.conn >= C_CONNECTED &&
+            os.disk == D_ATTACHING && ns.disk == D_NEGOTIATING) {
+                kfree(mdev->p_uuid); /* We expect to receive up-to-date UUIDs soon. */
+                mdev->p_uuid = NULL; /* ...to not use the old ones in the mean time */
+                drbd_send_sizes(mdev, 0);  /* to start sync... */
+                drbd_send_uuids(mdev);
+                drbd_send_state(mdev);
+        }
+
+        /* We want to pause/continue resync, tell peer. */
+        if (ns.conn >= C_CONNECTED &&
+             ((os.aftr_isp != ns.aftr_isp) ||
+              (os.user_isp != ns.user_isp)))
+                drbd_send_state(mdev);
+
+        /* In case one of the isp bits got set, suspend other devices. */
+        if ((!os.aftr_isp && !os.peer_isp && !os.user_isp) &&
+            (ns.aftr_isp || ns.peer_isp || ns.user_isp))
+                suspend_other_sg(mdev);
+
+        /* Make sure the peer gets informed about eventual state
+           changes (ISP bits) while we were in WFReportParams. */
+        if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
+                drbd_send_state(mdev);
+
+        /* We are in the progress to start a full sync... */
+        if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
+            (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
+                drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, &abw_start_sync, "set_n_write from StartingSync");
+
+        /* We are invalidating our self... */
+        if (os.conn < C_CONNECTED && ns.conn < C_CONNECTED &&
+            os.disk > D_INCONSISTENT && ns.disk == D_INCONSISTENT)
+                drbd_queue_bitmap_io(mdev, &drbd_bmio_set_n_write, NULL, "set_n_write from invalidate");
+
+        if (os.disk > D_FAILED && ns.disk == D_FAILED) {
+                enum drbd_io_error_p eh;
+
+                eh = EP_PASS_ON;
+                if (get_ldev_if_state(mdev, D_FAILED)) {
+                        eh = mdev->ldev->dc.on_io_error;
+                        put_ldev(mdev);
+                }
+
+                drbd_rs_cancel_all(mdev);
+                /* since get_ldev() only works as long as disk>=D_INCONSISTENT,
+                   and it is D_DISKLESS here, local_cnt can only go down, it can
+                   not increase... It will reach zero */
+                wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
+                mdev->rs_total = 0;
+                mdev->rs_failed = 0;
+                atomic_set(&mdev->rs_pending_cnt, 0);
+
+                spin_lock_irq(&mdev->req_lock);
+                _drbd_set_state(_NS(mdev, disk, D_DISKLESS), CS_HARD, NULL);
+                spin_unlock_irq(&mdev->req_lock);
+
+                if (eh == EP_CALL_HELPER)
+                        drbd_khelper(mdev, "local-io-error");
+        }
+
+        if (os.disk > D_DISKLESS && ns.disk == D_DISKLESS) {
+
+                if (os.disk == D_FAILED) /* && ns.disk == D_DISKLESS*/ {
+                        if (drbd_send_state(mdev))
+                                dev_warn(DEV, "Notified peer that my disk is broken.\n");
+                        else
+                                dev_err(DEV, "Sending state in drbd_io_error() failed\n");
+                }
+
+                lc_destroy(mdev->resync);
+                mdev->resync = NULL;
+                lc_destroy(mdev->act_log);
+                mdev->act_log = NULL;
+                __no_warn(local,
+                        drbd_free_bc(mdev->ldev);
+                        mdev->ldev = NULL;);
+
+                if (mdev->md_io_tmpp)
+                        __free_page(mdev->md_io_tmpp);
+        }
+
+        /* Disks got bigger while they were detached */
+        if (ns.disk > D_NEGOTIATING && ns.pdsk > D_NEGOTIATING &&
+            test_and_clear_bit(RESYNC_AFTER_NEG, &mdev->flags)) {
+                if (ns.conn == C_CONNECTED)
+                        resync_after_online_grow(mdev);
+        }
+
+        /* A resync finished or aborted, wake paused devices... */
+        if ((os.conn > C_CONNECTED && ns.conn <= C_CONNECTED) ||
+            (os.peer_isp && !ns.peer_isp) ||
+            (os.user_isp && !ns.user_isp))
+                resume_next_sg(mdev);
+
+        /* Upon network connection, we need to start the receiver */
+        if (os.conn == C_STANDALONE && ns.conn == C_UNCONNECTED)
+                drbd_thread_start(&mdev->receiver);
+
+        /* Terminate worker thread if we are unconfigured - it will be
+           restarted as needed... */
+        if (ns.disk == D_DISKLESS &&
+            ns.conn == C_STANDALONE &&
+            ns.role == R_SECONDARY) {
+                if (os.aftr_isp != ns.aftr_isp)
+                        resume_next_sg(mdev);
+                /* set in __drbd_set_state, unless CONFIG_PENDING was set */
+                if (test_bit(DEVICE_DYING, &mdev->flags))
+                        drbd_thread_stop_nowait(&mdev->worker);
+        }
+
+        drbd_md_sync(mdev);
+}
+
+
+static int drbd_thread_setup(void *arg)
+{
+        struct drbd_thread *thi = (struct drbd_thread *) arg;
+        struct drbd_conf *mdev = thi->mdev;
+        unsigned long flags;
+        int retval;
+
+restart:
+        retval = thi->function(thi);
+
+        spin_lock_irqsave(&thi->t_lock, flags);
+
+        /* if the receiver has been "Exiting", the last thing it did
+         * was set the conn state to "StandAlone",
+         * if now a re-connect request comes in, conn state goes C_UNCONNECTED,
+         * and receiver thread will be "started".
+         * drbd_thread_start needs to set "Restarting" in that case.
+         * t_state check and assignment needs to be within the same spinlock,
+         * so either thread_start sees Exiting, and can remap to Restarting,
+         * or thread_start see None, and can proceed as normal.
+         */
+
+        if (thi->t_state == Restarting) {
+                dev_info(DEV, "Restarting %s\n", current->comm);
+                thi->t_state = Running;
+                spin_unlock_irqrestore(&thi->t_lock, flags);
+                goto restart;
+        }
+
+        thi->task = NULL;
+        thi->t_state = None;
+        smp_mb();
+        complete(&thi->stop);
+        spin_unlock_irqrestore(&thi->t_lock, flags);
+
+        dev_info(DEV, "Terminating %s\n", current->comm);
+
+        /* Release mod reference taken when thread was started */
+        module_put(THIS_MODULE);
+        return retval;
+}
+
+static void drbd_thread_init(struct drbd_conf *mdev, struct drbd_thread *thi,
+                      int (*func) (struct drbd_thread *))
+{
+        spin_lock_init(&thi->t_lock);
+        thi->task    = NULL;
+        thi->t_state = None;
+        thi->function = func;
+        thi->mdev = mdev;
+}
+
+int drbd_thread_start(struct drbd_thread *thi)
+{
+        struct drbd_conf *mdev = thi->mdev;
+        struct task_struct *nt;
+        unsigned long flags;
+
+        const char *me =
+                thi == &mdev->receiver ? "receiver" :
+                thi == &mdev->asender  ? "asender"  :
+                thi == &mdev->worker   ? "worker"   : "NONSENSE";
+
+        /* is used from state engine doing drbd_thread_stop_nowait,
+         * while holding the req lock irqsave */
+        spin_lock_irqsave(&thi->t_lock, flags);
+
+        switch (thi->t_state) {
+        case None:
+                dev_info(DEV, "Starting %s thread (from %s [%d])\n",
+                                me, current->comm, current->pid);
+
+                /* Get ref on module for thread - this is released when thread exits */
+                if (!try_module_get(THIS_MODULE)) {
+                        dev_err(DEV, "Failed to get module reference in drbd_thread_start\n");
+                        spin_unlock_irqrestore(&thi->t_lock, flags);
+                        return FALSE;
+                }
+
+                init_completion(&thi->stop);
+                D_ASSERT(thi->task == NULL);
+                thi->reset_cpu_mask = 1;
+                thi->t_state = Running;
+                spin_unlock_irqrestore(&thi->t_lock, flags);
+                flush_signals(current); /* otherw. may get -ERESTARTNOINTR */
+
+                nt = kthread_create(drbd_thread_setup, (void *) thi,
+                                    "drbd%d_%s", mdev_to_minor(mdev), me);
+
+                if (IS_ERR(nt)) {
+                        dev_err(DEV, "Couldn't start thread\n");
+
+                        module_put(THIS_MODULE);
+                        return FALSE;
+                }
+                spin_lock_irqsave(&thi->t_lock, flags);
+                thi->task = nt;
+                thi->t_state = Running;
+                spin_unlock_irqrestore(&thi->t_lock, flags);
+                wake_up_process(nt);
+                break;
+        case Exiting:
+                thi->t_state = Restarting;
+                dev_info(DEV, "Restarting %s thread (from %s [%d])\n",
+                                me, current->comm, current->pid);
+                /* fall through */
+        case Running:
+        case Restarting:
+        default:
+                spin_unlock_irqrestore(&thi->t_lock, flags);
+                break;
+        }
+
+        return TRUE;
+}
+
+
+void _drbd_thread_stop(struct drbd_thread *thi, int restart, int wait)
+{
+        unsigned long flags;
+
+        enum drbd_thread_state ns = restart ? Restarting : Exiting;
+
+        /* may be called from state engine, holding the req lock irqsave */
+        spin_lock_irqsave(&thi->t_lock, flags);
+
+        if (thi->t_state == None) {
+                spin_unlock_irqrestore(&thi->t_lock, flags);
+                if (restart)
+                        drbd_thread_start(thi);
+                return;
+        }
+
+        if (thi->t_state != ns) {
+                if (thi->task == NULL) {
+                        spin_unlock_irqrestore(&thi->t_lock, flags);
+                        return;
+                }
+
+                thi->t_state = ns;
+                smp_mb();
+                init_completion(&thi->stop);
+                if (thi->task != current)
+                        force_sig(DRBD_SIGKILL, thi->task);
+
+        }
+
+        spin_unlock_irqrestore(&thi->t_lock, flags);
+
+        if (wait)
+                wait_for_completion(&thi->stop);
+}
+
+#ifdef CONFIG_SMP
+/**
+ * drbd_calc_cpu_mask() - Generate CPU masks, spread over all CPUs
+ * @mdev:       DRBD device.
+ *
+ * Forces all threads of a device onto the same CPU. This is beneficial for
+ * DRBD's performance. May be overwritten by user's configuration.
+ */
+void drbd_calc_cpu_mask(struct drbd_conf *mdev)
+{
+        int ord, cpu;
+
+        /* user override. */
+        if (cpumask_weight(mdev->cpu_mask))
+                return;
+
+        ord = mdev_to_minor(mdev) % cpumask_weight(cpu_online_mask);
+        for_each_online_cpu(cpu) {
+                if (ord-- == 0) {
+                        cpumask_set_cpu(cpu, mdev->cpu_mask);
+                        return;
+                }
+        }
+        /* should not be reached */
+        cpumask_setall(mdev->cpu_mask);
+}
+
+/**
+ * drbd_thread_current_set_cpu() - modifies the cpu mask of the _current_ thread
+ * @mdev:       DRBD device.
+ *
+ * call in the "main loop" of _all_ threads, no need for any mutex, current won't die
+ * prematurely.
+ */
+void drbd_thread_current_set_cpu(struct drbd_conf *mdev)
+{
+        struct task_struct *p = current;
+        struct drbd_thread *thi =
+                p == mdev->asender.task  ? &mdev->asender  :
+                p == mdev->receiver.task ? &mdev->receiver :
+                p == mdev->worker.task   ? &mdev->worker   :
+                NULL;
+        ERR_IF(thi == NULL)
+                return;
+        if (!thi->reset_cpu_mask)
+                return;
+        thi->reset_cpu_mask = 0;
+        set_cpus_allowed_ptr(p, mdev->cpu_mask);
+}
+#endif
+
+/* the appropriate socket mutex must be held already */
+int _drbd_send_cmd(struct drbd_conf *mdev, struct socket *sock,
+                          enum drbd_packets cmd, struct p_header *h,
+                          size_t size, unsigned msg_flags)
+{
+        int sent, ok;
+
+        ERR_IF(!h) return FALSE;
+        ERR_IF(!size) return FALSE;
+
+        h->magic   = BE_DRBD_MAGIC;
+        h->command = cpu_to_be16(cmd);
+        h->length  = cpu_to_be16(size-sizeof(struct p_header));
+
+        trace_drbd_packet(mdev, sock, 0, (void *)h, __FILE__, __LINE__);
+        sent = drbd_send(mdev, sock, h, size, msg_flags);
+
+        ok = (sent == size);
+        if (!ok)
+                dev_err(DEV, "short sent %s size=%d sent=%d\n",
+                    cmdname(cmd), (int)size, sent);
+        return ok;
+}
+
+/* don't pass the socket. we may only look at it
+ * when we hold the appropriate socket mutex.
+ */
+int drbd_send_cmd(struct drbd_conf *mdev, int use_data_socket,
+                  enum drbd_packets cmd, struct p_header *h, size_t size)
+{
+        int ok = 0;
+        struct socket *sock;
+
+        if (use_data_socket) {
+                mutex_lock(&mdev->data.mutex);
+                sock = mdev->data.socket;
+        } else {
+                mutex_lock(&mdev->meta.mutex);
+                sock = mdev->meta.socket;
+        }
+
+        /* drbd_disconnect() could have called drbd_free_sock()
+         * while we were waiting in down()... */
+        if (likely(sock != NULL))
+                ok = _drbd_send_cmd(mdev, sock, cmd, h, size, 0);
+
+        if (use_data_socket)
+                mutex_unlock(&mdev->data.mutex);
+        else
+                mutex_unlock(&mdev->meta.mutex);
+        return ok;
+}
+
+int drbd_send_cmd2(struct drbd_conf *mdev, enum drbd_packets cmd, char *data,
+                   size_t size)
+{
+        struct p_header h;
+        int ok;
+
+        h.magic   = BE_DRBD_MAGIC;
+        h.command = cpu_to_be16(cmd);
+        h.length  = cpu_to_be16(size);
+
+        if (!drbd_get_data_sock(mdev))
+                return 0;
+
+        trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&h, __FILE__, __LINE__);
+
+        ok = (sizeof(h) ==
+                drbd_send(mdev, mdev->data.socket, &h, sizeof(h), 0));
+        ok = ok && (size ==
+                drbd_send(mdev, mdev->data.socket, data, size, 0));
+
+        drbd_put_data_sock(mdev);
+
+        return ok;
+}
+
+int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc)
+{
+        struct p_rs_param_89 *p;
+        struct socket *sock;
+        int size, rv;
+        const int apv = mdev->agreed_pro_version;
+
+        size = apv <= 87 ? sizeof(struct p_rs_param)
+                : apv == 88 ? sizeof(struct p_rs_param)
+                        + strlen(mdev->sync_conf.verify_alg) + 1
+                : /* 89 */    sizeof(struct p_rs_param_89);
+
+        /* used from admin command context and receiver/worker context.
+         * to avoid kmalloc, grab the socket right here,
+         * then use the pre-allocated sbuf there */
+        mutex_lock(&mdev->data.mutex);
+        sock = mdev->data.socket;
+
+        if (likely(sock != NULL)) {
+                enum drbd_packets cmd = apv >= 89 ? P_SYNC_PARAM89 : P_SYNC_PARAM;
+
+                p = &mdev->data.sbuf.rs_param_89;
+
+                /* initialize verify_alg and csums_alg */
+                memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+                p->rate = cpu_to_be32(sc->rate);
+
+                if (apv >= 88)
+                        strcpy(p->verify_alg, mdev->sync_conf.verify_alg);
+                if (apv >= 89)
+                        strcpy(p->csums_alg, mdev->sync_conf.csums_alg);
+
+                rv = _drbd_send_cmd(mdev, sock, cmd, &p->head, size, 0);
+        } else
+                rv = 0; /* not ok */
+
+        mutex_unlock(&mdev->data.mutex);
+
+        return rv;
+}
+
+int drbd_send_protocol(struct drbd_conf *mdev)
+{
+        struct p_protocol *p;
+        int size, rv;
+
+        size = sizeof(struct p_protocol);
+
+        if (mdev->agreed_pro_version >= 87)
+                size += strlen(mdev->net_conf->integrity_alg) + 1;
+
+        /* we must not recurse into our own queue,
+         * as that is blocked during handshake */
+        p = kmalloc(size, GFP_NOIO);
+        if (p == NULL)
+                return 0;
+
+        p->protocol      = cpu_to_be32(mdev->net_conf->wire_protocol);
+        p->after_sb_0p   = cpu_to_be32(mdev->net_conf->after_sb_0p);
+        p->after_sb_1p   = cpu_to_be32(mdev->net_conf->after_sb_1p);
+        p->after_sb_2p   = cpu_to_be32(mdev->net_conf->after_sb_2p);
+        p->want_lose     = cpu_to_be32(mdev->net_conf->want_lose);
+        p->two_primaries = cpu_to_be32(mdev->net_conf->two_primaries);
+
+        if (mdev->agreed_pro_version >= 87)
+                strcpy(p->integrity_alg, mdev->net_conf->integrity_alg);
+
+        rv = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_PROTOCOL,
+                           (struct p_header *)p, size);
+        kfree(p);
+        return rv;
+}
+
+int _drbd_send_uuids(struct drbd_conf *mdev, u64 uuid_flags)
+{
+        struct p_uuids p;
+        int i;
+
+        if (!get_ldev_if_state(mdev, D_NEGOTIATING))
+                return 1;
+
+        for (i = UI_CURRENT; i < UI_SIZE; i++)
+                p.uuid[i] = mdev->ldev ? cpu_to_be64(mdev->ldev->md.uuid[i]) : 0;
+
+        mdev->comm_bm_set = drbd_bm_total_weight(mdev);
+        p.uuid[UI_SIZE] = cpu_to_be64(mdev->comm_bm_set);
+        uuid_flags |= mdev->net_conf->want_lose ? 1 : 0;
+        uuid_flags |= test_bit(CRASHED_PRIMARY, &mdev->flags) ? 2 : 0;
+        uuid_flags |= mdev->new_state_tmp.disk == D_INCONSISTENT ? 4 : 0;
+        p.uuid[UI_FLAGS] = cpu_to_be64(uuid_flags);
+
+        put_ldev(mdev);
+
+        return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_UUIDS,
+                             (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_uuids(struct drbd_conf *mdev)
+{
+        return _drbd_send_uuids(mdev, 0);
+}
+
+int drbd_send_uuids_skip_initial_sync(struct drbd_conf *mdev)
+{
+        return _drbd_send_uuids(mdev, 8);
+}
+
+
+int drbd_send_sync_uuid(struct drbd_conf *mdev, u64 val)
+{
+        struct p_rs_uuid p;
+
+        p.uuid = cpu_to_be64(val);
+
+        return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SYNC_UUID,
+                             (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_sizes(struct drbd_conf *mdev, int trigger_reply)
+{
+        struct p_sizes p;
+        sector_t d_size, u_size;
+        int q_order_type;
+        int ok;
+
+        if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                D_ASSERT(mdev->ldev->backing_bdev);
+                d_size = drbd_get_max_capacity(mdev->ldev);
+                u_size = mdev->ldev->dc.disk_size;
+                q_order_type = drbd_queue_order_type(mdev);
+                p.queue_order_type = cpu_to_be32(drbd_queue_order_type(mdev));
+                put_ldev(mdev);
+        } else {
+                d_size = 0;
+                u_size = 0;
+                q_order_type = QUEUE_ORDERED_NONE;
+        }
+
+        p.d_size = cpu_to_be64(d_size);
+        p.u_size = cpu_to_be64(u_size);
+        p.c_size = cpu_to_be64(trigger_reply ? 0 : drbd_get_capacity(mdev->this_bdev));
+        p.max_segment_size = cpu_to_be32(queue_max_segment_size(mdev->rq_queue));
+        p.queue_order_type = cpu_to_be32(q_order_type);
+
+        ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_SIZES,
+                           (struct p_header *)&p, sizeof(p));
+        return ok;
+}
+
+/**
+ * drbd_send_state() - Sends the drbd state to the peer
+ * @mdev:       DRBD device.
+ */
+int drbd_send_state(struct drbd_conf *mdev)
+{
+        struct socket *sock;
+        struct p_state p;
+        int ok = 0;
+
+        /* Grab state lock so we wont send state if we're in the middle
+         * of a cluster wide state change on another thread */
+        drbd_state_lock(mdev);
+
+        mutex_lock(&mdev->data.mutex);
+
+        p.state = cpu_to_be32(mdev->state.i); /* Within the send mutex */
+        sock = mdev->data.socket;
+
+        if (likely(sock != NULL)) {
+                ok = _drbd_send_cmd(mdev, sock, P_STATE,
+                                    (struct p_header *)&p, sizeof(p), 0);
+        }
+
+        mutex_unlock(&mdev->data.mutex);
+
+        drbd_state_unlock(mdev);
+        return ok;
+}
+
+int drbd_send_state_req(struct drbd_conf *mdev,
+        union drbd_state mask, union drbd_state val)
+{
+        struct p_req_state p;
+
+        p.mask    = cpu_to_be32(mask.i);
+        p.val     = cpu_to_be32(val.i);
+
+        return drbd_send_cmd(mdev, USE_DATA_SOCKET, P_STATE_CHG_REQ,
+                             (struct p_header *)&p, sizeof(p));
+}
+
+int drbd_send_sr_reply(struct drbd_conf *mdev, int retcode)
+{
+        struct p_req_state_reply p;
+
+        p.retcode    = cpu_to_be32(retcode);
+
+        return drbd_send_cmd(mdev, USE_META_SOCKET, P_STATE_CHG_REPLY,
+                             (struct p_header *)&p, sizeof(p));
+}
+
+int fill_bitmap_rle_bits(struct drbd_conf *mdev,
+        struct p_compressed_bm *p,
+        struct bm_xfer_ctx *c)
+{
+        struct bitstream bs;
+        unsigned long plain_bits;
+        unsigned long tmp;
+        unsigned long rl;
+        unsigned len;
+        unsigned toggle;
+        int bits;
+
+        /* may we use this feature? */
+        if ((mdev->sync_conf.use_rle == 0) ||
+                (mdev->agreed_pro_version < 90))
+                        return 0;
+
+        if (c->bit_offset >= c->bm_bits)
+                return 0; /* nothing to do. */
+
+        /* use at most thus many bytes */
+        bitstream_init(&bs, p->code, BM_PACKET_VLI_BYTES_MAX, 0);
+        memset(p->code, 0, BM_PACKET_VLI_BYTES_MAX);
+        /* plain bits covered in this code string */
+        plain_bits = 0;
+
+        /* p->encoding & 0x80 stores whether the first run length is set.
+         * bit offset is implicit.
+         * start with toggle == 2 to be able to tell the first iteration */
+        toggle = 2;
+
+        /* see how much plain bits we can stuff into one packet
+         * using RLE and VLI. */
+        do {
+                tmp = (toggle == 0) ? _drbd_bm_find_next_zero(mdev, c->bit_offset)
+                                    : _drbd_bm_find_next(mdev, c->bit_offset);
+                if (tmp == -1UL)
+                        tmp = c->bm_bits;
+                rl = tmp - c->bit_offset;
+
+                if (toggle == 2) { /* first iteration */
+                        if (rl == 0) {
+                                /* the first checked bit was set,
+                                 * store start value, */
+                                DCBP_set_start(p, 1);
+                                /* but skip encoding of zero run length */
+                                toggle = !toggle;
+                                continue;
+                        }
+                        DCBP_set_start(p, 0);
+                }
+
+                /* paranoia: catch zero runlength.
+                 * can only happen if bitmap is modified while we scan it. */
+                if (rl == 0) {
+                        dev_err(DEV, "unexpected zero runlength while encoding bitmap "
+                            "t:%u bo:%lu\n", toggle, c->bit_offset);
+                        return -1;
+                }
+
+                bits = vli_encode_bits(&bs, rl);
+                if (bits == -ENOBUFS) /* buffer full */
+                        break;
+                if (bits <= 0) {
+                        dev_err(DEV, "error while encoding bitmap: %d\n", bits);
+                        return 0;
+                }
+
+                toggle = !toggle;
+                plain_bits += rl;
+                c->bit_offset = tmp;
+        } while (c->bit_offset < c->bm_bits);
+
+        len = bs.cur.b - p->code + !!bs.cur.bit;
+
+        if (plain_bits < (len << 3)) {
+                /* incompressible with this method.
+                 * we need to rewind both word and bit position. */
+                c->bit_offset -= plain_bits;
+                bm_xfer_ctx_bit_to_word_offset(c);
+                c->bit_offset = c->word_offset * BITS_PER_LONG;
+                return 0;
+        }
+
+        /* RLE + VLI was able to compress it just fine.
+         * update c->word_offset. */
+        bm_xfer_ctx_bit_to_word_offset(c);
+
+        /* store pad_bits */
+        DCBP_set_pad_bits(p, (8 - bs.cur.bit) & 0x7);
+
+        return len;
+}
+
+enum { OK, FAILED, DONE }
+send_bitmap_rle_or_plain(struct drbd_conf *mdev,
+        struct p_header *h, struct bm_xfer_ctx *c)
+{
+        struct p_compressed_bm *p = (void*)h;
+        unsigned long num_words;
+        int len;
+        int ok;
+
+        len = fill_bitmap_rle_bits(mdev, p, c);
+
+        if (len < 0)
+                return FAILED;
+
+        if (len) {
+                DCBP_set_code(p, RLE_VLI_Bits);
+                ok = _drbd_send_cmd(mdev, mdev->data.socket, P_COMPRESSED_BITMAP, h,
+                        sizeof(*p) + len, 0);
+
+                c->packets[0]++;
+                c->bytes[0] += sizeof(*p) + len;
+
+                if (c->bit_offset >= c->bm_bits)
+                        len = 0; /* DONE */
+        } else {
+                /* was not compressible.
+                 * send a buffer full of plain text bits instead. */
+                num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+                len = num_words * sizeof(long);
+                if (len)
+                        drbd_bm_get_lel(mdev, c->word_offset, num_words, (unsigned long*)h->payload);
+                ok = _drbd_send_cmd(mdev, mdev->data.socket, P_BITMAP,
+                                   h, sizeof(struct p_header) + len, 0);
+                c->word_offset += num_words;
+                c->bit_offset = c->word_offset * BITS_PER_LONG;
+
+                c->packets[1]++;
+                c->bytes[1] += sizeof(struct p_header) + len;
+
+                if (c->bit_offset > c->bm_bits)
+                        c->bit_offset = c->bm_bits;
+        }
+        ok = ok ? ((len == 0) ? DONE : OK) : FAILED;
+
+        if (ok == DONE)
+                INFO_bm_xfer_stats(mdev, "send", c);
+        return ok;
+}
+
+/* See the comment at receive_bitmap() */
+int _drbd_send_bitmap(struct drbd_conf *mdev)
+{
+        struct bm_xfer_ctx c;
+        struct p_header *p;
+        int ret;
+
+        ERR_IF(!mdev->bitmap) return FALSE;
+
+        /* maybe we should use some per thread scratch page,
+         * and allocate that during initial device creation? */
+        p = (struct p_header *) __get_free_page(GFP_NOIO);
+        if (!p) {
+                dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+                return FALSE;
+        }
+
+        if (get_ldev(mdev)) {
+                if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
+                        dev_info(DEV, "Writing the whole bitmap, MDF_FullSync was set.\n");
+                        drbd_bm_set_all(mdev);
+                        if (drbd_bm_write(mdev)) {
+                                /* write_bm did fail! Leave full sync flag set in Meta P_DATA
+                                 * but otherwise process as per normal - need to tell other
+                                 * side that a full resync is required! */
+                                dev_err(DEV, "Failed to write bitmap to disk!\n");
+                        } else {
+                                drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
+                                drbd_md_sync(mdev);
+                        }
+                }
+                put_ldev(mdev);
+        }
+
+        c = (struct bm_xfer_ctx) {
+                .bm_bits = drbd_bm_bits(mdev),
+                .bm_words = drbd_bm_words(mdev),
+        };
+
+        do {
+                ret = send_bitmap_rle_or_plain(mdev, p, &c);
+        } while (ret == OK);
+
+        free_page((unsigned long) p);
+        return (ret == DONE);
+}
+
+int drbd_send_bitmap(struct drbd_conf *mdev)
+{
+        int err;
+
+        if (!drbd_get_data_sock(mdev))
+                return -1;
+        err = !_drbd_send_bitmap(mdev);
+        drbd_put_data_sock(mdev);
+        return err;
+}
+
+int drbd_send_b_ack(struct drbd_conf *mdev, u32 barrier_nr, u32 set_size)
+{
+        int ok;
+        struct p_barrier_ack p;
+
+        p.barrier  = barrier_nr;
+        p.set_size = cpu_to_be32(set_size);
+
+        if (mdev->state.conn < C_CONNECTED)
+                return FALSE;
+        ok = drbd_send_cmd(mdev, USE_META_SOCKET, P_BARRIER_ACK,
+                        (struct p_header *)&p, sizeof(p));
+        return ok;
+}
+
+/**
+ * _drbd_send_ack() - Sends an ack packet
+ * @mdev:       DRBD device.
+ * @cmd:        Packet command code.
+ * @sector:     sector, needs to be in big endian byte order
+ * @blksize:    size in byte, needs to be in big endian byte order
+ * @block_id:   Id, big endian byte order
+ */
+static int _drbd_send_ack(struct drbd_conf *mdev, enum drbd_packets cmd,
+                          u64 sector,
+                          u32 blksize,
+                          u64 block_id)
+{
+        int ok;
+        struct p_block_ack p;
+
+        p.sector   = sector;
+        p.block_id = block_id;
+        p.blksize  = blksize;
+        p.seq_num  = cpu_to_be32(atomic_add_return(1, &mdev->packet_seq));
+
+        if (!mdev->meta.socket || mdev->state.conn < C_CONNECTED)
+                return FALSE;
+        ok = drbd_send_cmd(mdev, USE_META_SOCKET, cmd,
+                                (struct p_header *)&p, sizeof(p));
+        return ok;
+}
+
+int drbd_send_ack_dp(struct drbd_conf *mdev, enum drbd_packets cmd,
+                     struct p_data *dp)
+{
+        const int header_size = sizeof(struct p_data)
+                              - sizeof(struct p_header);
+        int data_size  = ((struct p_header *)dp)->length - header_size;
+
+        return _drbd_send_ack(mdev, cmd, dp->sector, cpu_to_be32(data_size),
+                              dp->block_id);
+}
+
+int drbd_send_ack_rp(struct drbd_conf *mdev, enum drbd_packets cmd,
+                     struct p_block_req *rp)
+{
+        return _drbd_send_ack(mdev, cmd, rp->sector, rp->blksize, rp->block_id);
+}
+
+/**
+ * drbd_send_ack() - Sends an ack packet
+ * @mdev:       DRBD device.
+ * @cmd:        Packet command code.
+ * @e:          Epoch entry.
+ */
+int drbd_send_ack(struct drbd_conf *mdev,
+        enum drbd_packets cmd, struct drbd_epoch_entry *e)
+{
+        return _drbd_send_ack(mdev, cmd,
+                              cpu_to_be64(e->sector),
+                              cpu_to_be32(e->size),
+                              e->block_id);
+}
+
+/* This function misuses the block_id field to signal if the blocks
+ * are is sync or not. */
+int drbd_send_ack_ex(struct drbd_conf *mdev, enum drbd_packets cmd,
+                     sector_t sector, int blksize, u64 block_id)
+{
+        return _drbd_send_ack(mdev, cmd,
+                              cpu_to_be64(sector),
+                              cpu_to_be32(blksize),
+                              cpu_to_be64(block_id));
+}
+
+int drbd_send_drequest(struct drbd_conf *mdev, int cmd,
+                       sector_t sector, int size, u64 block_id)
+{
+        int ok;
+        struct p_block_req p;
+
+        p.sector   = cpu_to_be64(sector);
+        p.block_id = block_id;
+        p.blksize  = cpu_to_be32(size);
+
+        ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, cmd,
+                                (struct p_header *)&p, sizeof(p));
+        return ok;
+}
+
+int drbd_send_drequest_csum(struct drbd_conf *mdev,
+                            sector_t sector, int size,
+                            void *digest, int digest_size,
+                            enum drbd_packets cmd)
+{
+        int ok;
+        struct p_block_req p;
+
+        p.sector   = cpu_to_be64(sector);
+        p.block_id = BE_DRBD_MAGIC + 0xbeef;
+        p.blksize  = cpu_to_be32(size);
+
+        p.head.magic   = BE_DRBD_MAGIC;
+        p.head.command = cpu_to_be16(cmd);
+        p.head.length  = cpu_to_be16(sizeof(p) - sizeof(struct p_header) + digest_size);
+
+        mutex_lock(&mdev->data.mutex);
+
+        ok = (sizeof(p) == drbd_send(mdev, mdev->data.socket, &p, sizeof(p), 0));
+        ok = ok && (digest_size == drbd_send(mdev, mdev->data.socket, digest, digest_size, 0));
+
+        mutex_unlock(&mdev->data.mutex);
+
+        return ok;
+}
+
+int drbd_send_ov_request(struct drbd_conf *mdev, sector_t sector, int size)
+{
+        int ok;
+        struct p_block_req p;
+
+        p.sector   = cpu_to_be64(sector);
+        p.block_id = BE_DRBD_MAGIC + 0xbabe;
+        p.blksize  = cpu_to_be32(size);
+
+        ok = drbd_send_cmd(mdev, USE_DATA_SOCKET, P_OV_REQUEST,
+                           (struct p_header *)&p, sizeof(p));
+        return ok;
+}
+
+/* called on sndtimeo
+ * returns FALSE if we should retry,
+ * TRUE if we think connection is dead
+ */
+static int we_should_drop_the_connection(struct drbd_conf *mdev, struct socket *sock)
+{
+        int drop_it;
+        /* long elapsed = (long)(jiffies - mdev->last_received); */
+
+        drop_it =   mdev->meta.socket == sock
+                || !mdev->asender.task
+                || get_t_state(&mdev->asender) != Running
+                || mdev->state.conn < C_CONNECTED;
+
+        if (drop_it)
+                return TRUE;
+
+        drop_it = !--mdev->ko_count;
+        if (!drop_it) {
+                dev_err(DEV, "[%s/%d] sock_sendmsg time expired, ko = %u\n",
+                       current->comm, current->pid, mdev->ko_count);
+                request_ping(mdev);
+        }
+
+        return drop_it; /* && (mdev->state == R_PRIMARY) */;
+}
+
+/* The idea of sendpage seems to be to put some kind of reference
+ * to the page into the skb, and to hand it over to the NIC. In
+ * this process get_page() gets called.
+ *
+ * As soon as the page was really sent over the network put_page()
+ * gets called by some part of the network layer. [ NIC driver? ]
+ *
+ * [ get_page() / put_page() increment/decrement the count. If count
+ *   reaches 0 the page will be freed. ]
+ *
+ * This works nicely with pages from FSs.
+ * But this means that in protocol A we might signal IO completion too early!
+ *
+ * In order not to corrupt data during a resync we must make sure
+ * that we do not reuse our own buffer pages (EEs) to early, therefore
+ * we have the net_ee list.
+ *
+ * XFS seems to have problems, still, it submits pages with page_count == 0!
+ * As a workaround, we disable sendpage on pages
+ * with page_count == 0 or PageSlab.
+ */
+static int _drbd_no_send_page(struct drbd_conf *mdev, struct page *page,
+                   int offset, size_t size)
+{
+        int sent = drbd_send(mdev, mdev->data.socket, kmap(page) + offset, size, 0);
+        kunmap(page);
+        if (sent == size)
+                mdev->send_cnt += size>>9;
+        return sent == size;
+}
+
+static int _drbd_send_page(struct drbd_conf *mdev, struct page *page,
+                    int offset, size_t size)
+{
+        mm_segment_t oldfs = get_fs();
+        int sent, ok;
+        int len = size;
+
+        /* e.g. XFS meta- & log-data is in slab pages, which have a
+         * page_count of 0 and/or have PageSlab() set.
+         * we cannot use send_page for those, as that does get_page();
+         * put_page(); and would cause either a VM_BUG directly, or
+         * __page_cache_release a page that would actually still be referenced
+         * by someone, leading to some obscure delayed Oops somewhere else. */
+        if (disable_sendpage || (page_count(page) < 1) || PageSlab(page))
+                return _drbd_no_send_page(mdev, page, offset, size);
+
+        drbd_update_congested(mdev);
+        set_fs(KERNEL_DS);
+        do {
+                sent = mdev->data.socket->ops->sendpage(mdev->data.socket, page,
+                                                        offset, len,
+                                                        MSG_NOSIGNAL);
+                if (sent == -EAGAIN) {
+                        if (we_should_drop_the_connection(mdev,
+                                                          mdev->data.socket))
+                                break;
+                        else
+                                continue;
+                }
+                if (sent <= 0) {
+                        dev_warn(DEV, "%s: size=%d len=%d sent=%d\n",
+                             __func__, (int)size, len, sent);
+                        break;
+                }
+                len    -= sent;
+                offset += sent;
+        } while (len > 0 /* THINK && mdev->cstate >= C_CONNECTED*/);
+        set_fs(oldfs);
+        clear_bit(NET_CONGESTED, &mdev->flags);
+
+        ok = (len == 0);
+        if (likely(ok))
+                mdev->send_cnt += size>>9;
+        return ok;
+}
+
+static int _drbd_send_bio(struct drbd_conf *mdev, struct bio *bio)
+{
+        struct bio_vec *bvec;
+        int i;
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                if (!_drbd_no_send_page(mdev, bvec->bv_page,
+                                     bvec->bv_offset, bvec->bv_len))
+                        return 0;
+        }
+        return 1;
+}
+
+static int _drbd_send_zc_bio(struct drbd_conf *mdev, struct bio *bio)
+{
+        struct bio_vec *bvec;
+        int i;
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                if (!_drbd_send_page(mdev, bvec->bv_page,
+                                     bvec->bv_offset, bvec->bv_len))
+                        return 0;
+        }
+
+        return 1;
+}
+
+/* Used to send write requests
+ * R_PRIMARY -> Peer    (P_DATA)
+ */
+int drbd_send_dblock(struct drbd_conf *mdev, struct drbd_request *req)
+{
+        int ok = 1;
+        struct p_data p;
+        unsigned int dp_flags = 0;
+        void *dgb;
+        int dgs;
+
+        if (!drbd_get_data_sock(mdev))
+                return 0;
+
+        dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+                crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+        p.head.magic   = BE_DRBD_MAGIC;
+        p.head.command = cpu_to_be16(P_DATA);
+        p.head.length  =
+                cpu_to_be16(sizeof(p) - sizeof(struct p_header) + dgs + req->size);
+
+        p.sector   = cpu_to_be64(req->sector);
+        p.block_id = (unsigned long)req;
+        p.seq_num  = cpu_to_be32(req->seq_num =
+                                 atomic_add_return(1, &mdev->packet_seq));
+        dp_flags = 0;
+
+        /* NOTE: no need to check if barriers supported here as we would
+         *       not pass the test in make_request_common in that case
+         */
+        if (bio_rw_flagged(req->master_bio, BIO_RW_BARRIER)) {
+                dev_err(DEV, "ASSERT FAILED would have set DP_HARDBARRIER\n");
+                /* dp_flags |= DP_HARDBARRIER; */
+        }
+        if (bio_rw_flagged(req->master_bio, BIO_RW_SYNCIO))
+                dp_flags |= DP_RW_SYNC;
+        /* for now handle SYNCIO and UNPLUG
+         * as if they still were one and the same flag */
+        if (bio_rw_flagged(req->master_bio, BIO_RW_UNPLUG))
+                dp_flags |= DP_RW_SYNC;
+        if (mdev->state.conn >= C_SYNC_SOURCE &&
+            mdev->state.conn <= C_PAUSED_SYNC_T)
+                dp_flags |= DP_MAY_SET_IN_SYNC;
+
+        p.dp_flags = cpu_to_be32(dp_flags);
+        trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&p, __FILE__, __LINE__);
+        set_bit(UNPLUG_REMOTE, &mdev->flags);
+        ok = (sizeof(p) ==
+                drbd_send(mdev, mdev->data.socket, &p, sizeof(p), MSG_MORE));
+        if (ok && dgs) {
+                dgb = mdev->int_dig_out;
+                drbd_csum(mdev, mdev->integrity_w_tfm, req->master_bio, dgb);
+                ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
+        }
+        if (ok) {
+                if (mdev->net_conf->wire_protocol == DRBD_PROT_A)
+                        ok = _drbd_send_bio(mdev, req->master_bio);
+                else
+                        ok = _drbd_send_zc_bio(mdev, req->master_bio);
+        }
+
+        drbd_put_data_sock(mdev);
+        return ok;
+}
+
+/* answer packet, used to send data back for read requests:
+ *  Peer       -> (diskless) R_PRIMARY   (P_DATA_REPLY)
+ *  C_SYNC_SOURCE -> C_SYNC_TARGET         (P_RS_DATA_REPLY)
+ */
+int drbd_send_block(struct drbd_conf *mdev, enum drbd_packets cmd,
+                    struct drbd_epoch_entry *e)
+{
+        int ok;
+        struct p_data p;
+        void *dgb;
+        int dgs;
+
+        dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_w_tfm) ?
+                crypto_hash_digestsize(mdev->integrity_w_tfm) : 0;
+
+        p.head.magic   = BE_DRBD_MAGIC;
+        p.head.command = cpu_to_be16(cmd);
+        p.head.length  =
+                cpu_to_be16(sizeof(p) - sizeof(struct p_header) + dgs + e->size);
+
+        p.sector   = cpu_to_be64(e->sector);
+        p.block_id = e->block_id;
+        /* p.seq_num  = 0;    No sequence numbers here.. */
+
+        /* Only called by our kernel thread.
+         * This one may be interrupted by DRBD_SIG and/or DRBD_SIGKILL
+         * in response to admin command or module unload.
+         */
+        if (!drbd_get_data_sock(mdev))
+                return 0;
+
+        trace_drbd_packet(mdev, mdev->data.socket, 0, (void *)&p, __FILE__, __LINE__);
+        ok = sizeof(p) == drbd_send(mdev, mdev->data.socket, &p,
+                                        sizeof(p), MSG_MORE);
+        if (ok && dgs) {
+                dgb = mdev->int_dig_out;
+                drbd_csum(mdev, mdev->integrity_w_tfm, e->private_bio, dgb);
+                ok = drbd_send(mdev, mdev->data.socket, dgb, dgs, MSG_MORE);
+        }
+        if (ok)
+                ok = _drbd_send_zc_bio(mdev, e->private_bio);
+
+        drbd_put_data_sock(mdev);
+        return ok;
+}
+
+/*
+  drbd_send distinguishes two cases:
+
+  Packets sent via the data socket "sock"
+  and packets sent via the meta data socket "msock"
+
+                    sock                      msock
+  -----------------+-------------------------+------------------------------
+  timeout           conf.timeout / 2          conf.timeout / 2
+  timeout action    send a ping via msock     Abort communication
+                                              and close all sockets
+*/
+
+/*
+ * you must have down()ed the appropriate [m]sock_mutex elsewhere!
+ */
+int drbd_send(struct drbd_conf *mdev, struct socket *sock,
+              void *buf, size_t size, unsigned msg_flags)
+{
+        struct kvec iov;
+        struct msghdr msg;
+        int rv, sent = 0;
+
+        if (!sock)
+                return -1000;
+
+        /* THINK  if (signal_pending) return ... ? */
+
+        iov.iov_base = buf;
+        iov.iov_len  = size;
+
+        msg.msg_name       = NULL;
+        msg.msg_namelen    = 0;
+        msg.msg_control    = NULL;
+        msg.msg_controllen = 0;
+        msg.msg_flags      = msg_flags | MSG_NOSIGNAL;
+
+        if (sock == mdev->data.socket) {
+                mdev->ko_count = mdev->net_conf->ko_count;
+                drbd_update_congested(mdev);
+        }
+        do {
+                /* STRANGE
+                 * tcp_sendmsg does _not_ use its size parameter at all ?
+                 *
+                 * -EAGAIN on timeout, -EINTR on signal.
+                 */
+/* THINK
+ * do we need to block DRBD_SIG if sock == &meta.socket ??
+ * otherwise wake_asender() might interrupt some send_*Ack !
+ */
+                rv = kernel_sendmsg(sock, &msg, &iov, 1, size);
+                if (rv == -EAGAIN) {
+                        if (we_should_drop_the_connection(mdev, sock))
+                                break;
+                        else
+                                continue;
+                }
+                D_ASSERT(rv != 0);
+                if (rv == -EINTR) {
+                        flush_signals(current);
+                        rv = 0;
+                }
+                if (rv < 0)
+                        break;
+                sent += rv;
+                iov.iov_base += rv;
+                iov.iov_len  -= rv;
+        } while (sent < size);
+
+        if (sock == mdev->data.socket)
+                clear_bit(NET_CONGESTED, &mdev->flags);
+
+        if (rv <= 0) {
+                if (rv != -EAGAIN) {
+                        dev_err(DEV, "%s_sendmsg returned %d\n",
+                            sock == mdev->meta.socket ? "msock" : "sock",
+                            rv);
+                        drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+                } else
+                        drbd_force_state(mdev, NS(conn, C_TIMEOUT));
+        }
+
+        return sent;
+}
+
+static int drbd_open(struct block_device *bdev, fmode_t mode)
+{
+        struct drbd_conf *mdev = bdev->bd_disk->private_data;
+        unsigned long flags;
+        int rv = 0;
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        /* to have a stable mdev->state.role
+         * and no race with updating open_cnt */
+
+        if (mdev->state.role != R_PRIMARY) {
+                if (mode & FMODE_WRITE)
+                        rv = -EROFS;
+                else if (!allow_oos)
+                        rv = -EMEDIUMTYPE;
+        }
+
+        if (!rv)
+                mdev->open_cnt++;
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        return rv;
+}
+
+static int drbd_release(struct gendisk *gd, fmode_t mode)
+{
+        struct drbd_conf *mdev = gd->private_data;
+        mdev->open_cnt--;
+        return 0;
+}
+
+static void drbd_unplug_fn(struct request_queue *q)
+{
+        struct drbd_conf *mdev = q->queuedata;
+
+        trace_drbd_unplug(mdev, "got unplugged");
+
+        /* unplug FIRST */
+        spin_lock_irq(q->queue_lock);
+        blk_remove_plug(q);
+        spin_unlock_irq(q->queue_lock);
+
+        /* only if connected */
+        spin_lock_irq(&mdev->req_lock);
+        if (mdev->state.pdsk >= D_INCONSISTENT && mdev->state.conn >= C_CONNECTED) {
+                D_ASSERT(mdev->state.role == R_PRIMARY);
+                if (test_and_clear_bit(UNPLUG_REMOTE, &mdev->flags)) {
+                        /* add to the data.work queue,
+                         * unless already queued.
+                         * XXX this might be a good addition to drbd_queue_work
+                         * anyways, to detect "double queuing" ... */
+                        if (list_empty(&mdev->unplug_work.list))
+                                drbd_queue_work(&mdev->data.work,
+                                                &mdev->unplug_work);
+                }
+        }
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (mdev->state.disk >= D_INCONSISTENT)
+                drbd_kick_lo(mdev);
+}
+
+static void drbd_set_defaults(struct drbd_conf *mdev)
+{
+        mdev->sync_conf.after      = DRBD_AFTER_DEF;
+        mdev->sync_conf.rate       = DRBD_RATE_DEF;
+        mdev->sync_conf.al_extents = DRBD_AL_EXTENTS_DEF;
+        mdev->state = (union drbd_state) {
+                { .role = R_SECONDARY,
+                  .peer = R_UNKNOWN,
+                  .conn = C_STANDALONE,
+                  .disk = D_DISKLESS,
+                  .pdsk = D_UNKNOWN,
+                  .susp = 0
+                } };
+}
+
+void drbd_init_set_defaults(struct drbd_conf *mdev)
+{
+        /* the memset(,0,) did most of this.
+         * note: only assignments, no allocation in here */
+
+        drbd_set_defaults(mdev);
+
+        /* for now, we do NOT yet support it,
+         * even though we start some framework
+         * to eventually support barriers */
+        set_bit(NO_BARRIER_SUPP, &mdev->flags);
+
+        atomic_set(&mdev->ap_bio_cnt, 0);
+        atomic_set(&mdev->ap_pending_cnt, 0);
+        atomic_set(&mdev->rs_pending_cnt, 0);
+        atomic_set(&mdev->unacked_cnt, 0);
+        atomic_set(&mdev->local_cnt, 0);
+        atomic_set(&mdev->net_cnt, 0);
+        atomic_set(&mdev->packet_seq, 0);
+        atomic_set(&mdev->pp_in_use, 0);
+
+        mutex_init(&mdev->md_io_mutex);
+        mutex_init(&mdev->data.mutex);
+        mutex_init(&mdev->meta.mutex);
+        sema_init(&mdev->data.work.s, 0);
+        sema_init(&mdev->meta.work.s, 0);
+        mutex_init(&mdev->state_mutex);
+
+        spin_lock_init(&mdev->data.work.q_lock);
+        spin_lock_init(&mdev->meta.work.q_lock);
+
+        spin_lock_init(&mdev->al_lock);
+        spin_lock_init(&mdev->req_lock);
+        spin_lock_init(&mdev->peer_seq_lock);
+        spin_lock_init(&mdev->epoch_lock);
+
+        INIT_LIST_HEAD(&mdev->active_ee);
+        INIT_LIST_HEAD(&mdev->sync_ee);
+        INIT_LIST_HEAD(&mdev->done_ee);
+        INIT_LIST_HEAD(&mdev->read_ee);
+        INIT_LIST_HEAD(&mdev->net_ee);
+        INIT_LIST_HEAD(&mdev->resync_reads);
+        INIT_LIST_HEAD(&mdev->data.work.q);
+        INIT_LIST_HEAD(&mdev->meta.work.q);
+        INIT_LIST_HEAD(&mdev->resync_work.list);
+        INIT_LIST_HEAD(&mdev->unplug_work.list);
+        INIT_LIST_HEAD(&mdev->md_sync_work.list);
+        INIT_LIST_HEAD(&mdev->bm_io_work.w.list);
+        mdev->resync_work.cb  = w_resync_inactive;
+        mdev->unplug_work.cb  = w_send_write_hint;
+        mdev->md_sync_work.cb = w_md_sync;
+        mdev->bm_io_work.w.cb = w_bitmap_io;
+        init_timer(&mdev->resync_timer);
+        init_timer(&mdev->md_sync_timer);
+        mdev->resync_timer.function = resync_timer_fn;
+        mdev->resync_timer.data = (unsigned long) mdev;
+        mdev->md_sync_timer.function = md_sync_timer_fn;
+        mdev->md_sync_timer.data = (unsigned long) mdev;
+
+        init_waitqueue_head(&mdev->misc_wait);
+        init_waitqueue_head(&mdev->state_wait);
+        init_waitqueue_head(&mdev->ee_wait);
+        init_waitqueue_head(&mdev->al_wait);
+        init_waitqueue_head(&mdev->seq_wait);
+
+        drbd_thread_init(mdev, &mdev->receiver, drbdd_init);
+        drbd_thread_init(mdev, &mdev->worker, drbd_worker);
+        drbd_thread_init(mdev, &mdev->asender, drbd_asender);
+
+        mdev->agreed_pro_version = PRO_VERSION_MAX;
+        mdev->write_ordering = WO_bio_barrier;
+        mdev->resync_wenr = LC_FREE;
+}
+
+void drbd_mdev_cleanup(struct drbd_conf *mdev)
+{
+        if (mdev->receiver.t_state != None)
+                dev_err(DEV, "ASSERT FAILED: receiver t_state == %d expected 0.\n",
+                                mdev->receiver.t_state);
+
+        /* no need to lock it, I'm the only thread alive */
+        if (atomic_read(&mdev->current_epoch->epoch_size) !=  0)
+                dev_err(DEV, "epoch_size:%d\n", atomic_read(&mdev->current_epoch->epoch_size));
+        mdev->al_writ_cnt  =
+        mdev->bm_writ_cnt  =
+        mdev->read_cnt     =
+        mdev->recv_cnt     =
+        mdev->send_cnt     =
+        mdev->writ_cnt     =
+        mdev->p_size       =
+        mdev->rs_start     =
+        mdev->rs_total     =
+        mdev->rs_failed    =
+        mdev->rs_mark_left =
+        mdev->rs_mark_time = 0;
+        D_ASSERT(mdev->net_conf == NULL);
+
+        drbd_set_my_capacity(mdev, 0);
+        if (mdev->bitmap) {
+                /* maybe never allocated. */
+                drbd_bm_resize(mdev, 0);
+                drbd_bm_cleanup(mdev);
+        }
+
+        drbd_free_resources(mdev);
+
+        /*
+         * currently we drbd_init_ee only on module load, so
+         * we may do drbd_release_ee only on module unload!
+         */
+        D_ASSERT(list_empty(&mdev->active_ee));
+        D_ASSERT(list_empty(&mdev->sync_ee));
+        D_ASSERT(list_empty(&mdev->done_ee));
+        D_ASSERT(list_empty(&mdev->read_ee));
+        D_ASSERT(list_empty(&mdev->net_ee));
+        D_ASSERT(list_empty(&mdev->resync_reads));
+        D_ASSERT(list_empty(&mdev->data.work.q));
+        D_ASSERT(list_empty(&mdev->meta.work.q));
+        D_ASSERT(list_empty(&mdev->resync_work.list));
+        D_ASSERT(list_empty(&mdev->unplug_work.list));
+
+}
+
+
+static void drbd_destroy_mempools(void)
+{
+        struct page *page;
+
+        while (drbd_pp_pool) {
+                page = drbd_pp_pool;
+                drbd_pp_pool = (struct page *)page_private(page);
+                __free_page(page);
+                drbd_pp_vacant--;
+        }
+
+        /* D_ASSERT(atomic_read(&drbd_pp_vacant)==0); */
+
+        if (drbd_ee_mempool)
+                mempool_destroy(drbd_ee_mempool);
+        if (drbd_request_mempool)
+                mempool_destroy(drbd_request_mempool);
+        if (drbd_ee_cache)
+                kmem_cache_destroy(drbd_ee_cache);
+        if (drbd_request_cache)
+                kmem_cache_destroy(drbd_request_cache);
+        if (drbd_bm_ext_cache)
+                kmem_cache_destroy(drbd_bm_ext_cache);
+        if (drbd_al_ext_cache)
+                kmem_cache_destroy(drbd_al_ext_cache);
+
+        drbd_ee_mempool      = NULL;
+        drbd_request_mempool = NULL;
+        drbd_ee_cache        = NULL;
+        drbd_request_cache   = NULL;
+        drbd_bm_ext_cache    = NULL;
+        drbd_al_ext_cache    = NULL;
+
+        return;
+}
+
+static int drbd_create_mempools(void)
+{
+        struct page *page;
+        const int number = (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE) * minor_count;
+        int i;
+
+        /* prepare our caches and mempools */
+        drbd_request_mempool = NULL;
+        drbd_ee_cache        = NULL;
+        drbd_request_cache   = NULL;
+        drbd_bm_ext_cache    = NULL;
+        drbd_al_ext_cache    = NULL;
+        drbd_pp_pool         = NULL;
+
+        /* caches */
+        drbd_request_cache = kmem_cache_create(
+                "drbd_req", sizeof(struct drbd_request), 0, 0, NULL);
+        if (drbd_request_cache == NULL)
+                goto Enomem;
+
+        drbd_ee_cache = kmem_cache_create(
+                "drbd_ee", sizeof(struct drbd_epoch_entry), 0, 0, NULL);
+        if (drbd_ee_cache == NULL)
+                goto Enomem;
+
+        drbd_bm_ext_cache = kmem_cache_create(
+                "drbd_bm", sizeof(struct bm_extent), 0, 0, NULL);
+        if (drbd_bm_ext_cache == NULL)
+                goto Enomem;
+
+        drbd_al_ext_cache = kmem_cache_create(
+                "drbd_al", sizeof(struct lc_element), 0, 0, NULL);
+        if (drbd_al_ext_cache == NULL)
+                goto Enomem;
+
+        /* mempools */
+        drbd_request_mempool = mempool_create(number,
+                mempool_alloc_slab, mempool_free_slab, drbd_request_cache);
+        if (drbd_request_mempool == NULL)
+                goto Enomem;
+
+        drbd_ee_mempool = mempool_create(number,
+                mempool_alloc_slab, mempool_free_slab, drbd_ee_cache);
+        if (drbd_request_mempool == NULL)
+                goto Enomem;
+
+        /* drbd's page pool */
+        spin_lock_init(&drbd_pp_lock);
+
+        for (i = 0; i < number; i++) {
+                page = alloc_page(GFP_HIGHUSER);
+                if (!page)
+                        goto Enomem;
+                set_page_private(page, (unsigned long)drbd_pp_pool);
+                drbd_pp_pool = page;
+        }
+        drbd_pp_vacant = number;
+
+        return 0;
+
+Enomem:
+        drbd_destroy_mempools(); /* in case we allocated some */
+        return -ENOMEM;
+}
+
+static int drbd_notify_sys(struct notifier_block *this, unsigned long code,
+        void *unused)
+{
+        /* just so we have it.  you never know what interesting things we
+         * might want to do here some day...
+         */
+
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block drbd_notifier = {
+        .notifier_call = drbd_notify_sys,
+};
+
+static void drbd_release_ee_lists(struct drbd_conf *mdev)
+{
+        int rr;
+
+        rr = drbd_release_ee(mdev, &mdev->active_ee);
+        if (rr)
+                dev_err(DEV, "%d EEs in active list found!\n", rr);
+
+        rr = drbd_release_ee(mdev, &mdev->sync_ee);
+        if (rr)
+                dev_err(DEV, "%d EEs in sync list found!\n", rr);
+
+        rr = drbd_release_ee(mdev, &mdev->read_ee);
+        if (rr)
+                dev_err(DEV, "%d EEs in read list found!\n", rr);
+
+        rr = drbd_release_ee(mdev, &mdev->done_ee);
+        if (rr)
+                dev_err(DEV, "%d EEs in done list found!\n", rr);
+
+        rr = drbd_release_ee(mdev, &mdev->net_ee);
+        if (rr)
+                dev_err(DEV, "%d EEs in net list found!\n", rr);
+}
+
+/* caution. no locking.
+ * currently only used from module cleanup code. */
+static void drbd_delete_device(unsigned int minor)
+{
+        struct drbd_conf *mdev = minor_to_mdev(minor);
+
+        if (!mdev)
+                return;
+
+        /* paranoia asserts */
+        if (mdev->open_cnt != 0)
+                dev_err(DEV, "open_cnt = %d in %s:%u", mdev->open_cnt,
+                                __FILE__ , __LINE__);
+
+        ERR_IF (!list_empty(&mdev->data.work.q)) {
+                struct list_head *lp;
+                list_for_each(lp, &mdev->data.work.q) {
+                        dev_err(DEV, "lp = %p\n", lp);
+                }
+        };
+        /* end paranoia asserts */
+
+        del_gendisk(mdev->vdisk);
+
+        /* cleanup stuff that may have been allocated during
+         * device (re-)configuration or state changes */
+
+        if (mdev->this_bdev)
+                bdput(mdev->this_bdev);
+
+        drbd_free_resources(mdev);
+
+        drbd_release_ee_lists(mdev);
+
+        /* should be free'd on disconnect? */
+        kfree(mdev->ee_hash);
+        /*
+        mdev->ee_hash_s = 0;
+        mdev->ee_hash = NULL;
+        */
+
+        lc_destroy(mdev->act_log);
+        lc_destroy(mdev->resync);
+
+        kfree(mdev->p_uuid);
+        /* mdev->p_uuid = NULL; */
+
+        kfree(mdev->int_dig_out);
+        kfree(mdev->int_dig_in);
+        kfree(mdev->int_dig_vv);
+
+        /* cleanup the rest that has been
+         * allocated from drbd_new_device
+         * and actually free the mdev itself */
+        drbd_free_mdev(mdev);
+}
+
+static void drbd_cleanup(void)
+{
+        unsigned int i;
+
+        unregister_reboot_notifier(&drbd_notifier);
+
+        drbd_nl_cleanup();
+
+        if (minor_table) {
+                if (drbd_proc)
+                        remove_proc_entry("drbd", NULL);
+                i = minor_count;
+                while (i--)
+                        drbd_delete_device(i);
+                drbd_destroy_mempools();
+        }
+
+        kfree(minor_table);
+
+        unregister_blkdev(DRBD_MAJOR, "drbd");
+
+        printk(KERN_INFO "drbd: module cleanup done.\n");
+}
+
+/**
+ * drbd_congested() - Callback for pdflush
+ * @congested_data:     User data
+ * @bdi_bits:           Bits pdflush is currently interested in
+ *
+ * Returns 1<<BDI_async_congested and/or 1<<BDI_sync_congested if we are congested.
+ */
+static int drbd_congested(void *congested_data, int bdi_bits)
+{
+        struct drbd_conf *mdev = congested_data;
+        struct request_queue *q;
+        char reason = '-';
+        int r = 0;
+
+        if (!__inc_ap_bio_cond(mdev)) {
+                /* DRBD has frozen IO */
+                r = bdi_bits;
+                reason = 'd';
+                goto out;
+        }
+
+        if (get_ldev(mdev)) {
+                q = bdev_get_queue(mdev->ldev->backing_bdev);
+                r = bdi_congested(&q->backing_dev_info, bdi_bits);
+                put_ldev(mdev);
+                if (r)
+                        reason = 'b';
+        }
+
+        if (bdi_bits & (1 << BDI_async_congested) && test_bit(NET_CONGESTED, &mdev->flags)) {
+                r |= (1 << BDI_async_congested);
+                reason = reason == 'b' ? 'a' : 'n';
+        }
+
+out:
+        mdev->congestion_reason = reason;
+        return r;
+}
+
+struct drbd_conf *drbd_new_device(unsigned int minor)
+{
+        struct drbd_conf *mdev;
+        struct gendisk *disk;
+        struct request_queue *q;
+
+        /* GFP_KERNEL, we are outside of all write-out paths */
+        mdev = kzalloc(sizeof(struct drbd_conf), GFP_KERNEL);
+        if (!mdev)
+                return NULL;
+        if (!zalloc_cpumask_var(&mdev->cpu_mask, GFP_KERNEL))
+                goto out_no_cpumask;
+
+        mdev->minor = minor;
+
+        drbd_init_set_defaults(mdev);
+
+        q = blk_alloc_queue(GFP_KERNEL);
+        if (!q)
+                goto out_no_q;
+        mdev->rq_queue = q;
+        q->queuedata   = mdev;
+        blk_queue_max_segment_size(q, DRBD_MAX_SEGMENT_SIZE);
+
+        disk = alloc_disk(1);
+        if (!disk)
+                goto out_no_disk;
+        mdev->vdisk = disk;
+
+        set_disk_ro(disk, TRUE);
+
+        disk->queue = q;
+        disk->major = DRBD_MAJOR;
+        disk->first_minor = minor;
+        disk->fops = &drbd_ops;
+        sprintf(disk->disk_name, "drbd%d", minor);
+        disk->private_data = mdev;
+
+        mdev->this_bdev = bdget(MKDEV(DRBD_MAJOR, minor));
+        /* we have no partitions. we contain only ourselves. */
+        mdev->this_bdev->bd_contains = mdev->this_bdev;
+
+        q->backing_dev_info.congested_fn = drbd_congested;
+        q->backing_dev_info.congested_data = mdev;
+
+        blk_queue_make_request(q, drbd_make_request_26);
+        blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
+        blk_queue_merge_bvec(q, drbd_merge_bvec);
+        q->queue_lock = &mdev->req_lock; /* needed since we use */
+                /* plugging on a queue, that actually has no requests! */
+        q->unplug_fn = drbd_unplug_fn;
+
+        mdev->md_io_page = alloc_page(GFP_KERNEL);
+        if (!mdev->md_io_page)
+                goto out_no_io_page;
+
+        if (drbd_bm_init(mdev))
+                goto out_no_bitmap;
+        /* no need to lock access, we are still initializing this minor device. */
+        if (!tl_init(mdev))
+                goto out_no_tl;
+
+        mdev->app_reads_hash = kzalloc(APP_R_HSIZE*sizeof(void *), GFP_KERNEL);
+        if (!mdev->app_reads_hash)
+                goto out_no_app_reads;
+
+        mdev->current_epoch = kzalloc(sizeof(struct drbd_epoch), GFP_KERNEL);
+        if (!mdev->current_epoch)
+                goto out_no_epoch;
+
+        INIT_LIST_HEAD(&mdev->current_epoch->list);
+        mdev->epochs = 1;
+
+        return mdev;
+
+/* out_whatever_else:
+        kfree(mdev->current_epoch); */
+out_no_epoch:
+        kfree(mdev->app_reads_hash);
+out_no_app_reads:
+        tl_cleanup(mdev);
+out_no_tl:
+        drbd_bm_cleanup(mdev);
+out_no_bitmap:
+        __free_page(mdev->md_io_page);
+out_no_io_page:
+        put_disk(disk);
+out_no_disk:
+        blk_cleanup_queue(q);
+out_no_q:
+        free_cpumask_var(mdev->cpu_mask);
+out_no_cpumask:
+        kfree(mdev);
+        return NULL;
+}
+
+/* counterpart of drbd_new_device.
+ * last part of drbd_delete_device. */
+void drbd_free_mdev(struct drbd_conf *mdev)
+{
+        kfree(mdev->current_epoch);
+        kfree(mdev->app_reads_hash);
+        tl_cleanup(mdev);
+        if (mdev->bitmap) /* should no longer be there. */
+                drbd_bm_cleanup(mdev);
+        __free_page(mdev->md_io_page);
+        put_disk(mdev->vdisk);
+        blk_cleanup_queue(mdev->rq_queue);
+        free_cpumask_var(mdev->cpu_mask);
+        kfree(mdev);
+}
+
+
+int __init drbd_init(void)
+{
+        int err;
+
+        if (sizeof(struct p_handshake) != 80) {
+                printk(KERN_ERR
+                       "drbd: never change the size or layout "
+                       "of the HandShake packet.\n");
+                return -EINVAL;
+        }
+
+        if (1 > minor_count || minor_count > 255) {
+                printk(KERN_ERR
+                        "drbd: invalid minor_count (%d)\n", minor_count);
+#ifdef MODULE
+                return -EINVAL;
+#else
+                minor_count = 8;
+#endif
+        }
+
+        err = drbd_nl_init();
+        if (err)
+                return err;
+
+        err = register_blkdev(DRBD_MAJOR, "drbd");
+        if (err) {
+                printk(KERN_ERR
+                       "drbd: unable to register block device major %d\n",
+                       DRBD_MAJOR);
+                return err;
+        }
+
+        register_reboot_notifier(&drbd_notifier);
+
+        /*
+         * allocate all necessary structs
+         */
+        err = -ENOMEM;
+
+        init_waitqueue_head(&drbd_pp_wait);
+
+        drbd_proc = NULL; /* play safe for drbd_cleanup */
+        minor_table = kzalloc(sizeof(struct drbd_conf *)*minor_count,
+                                GFP_KERNEL);
+        if (!minor_table)
+                goto Enomem;
+
+        err = drbd_create_mempools();
+        if (err)
+                goto Enomem;
+
+        drbd_proc = proc_create("drbd", S_IFREG | S_IRUGO , NULL, &drbd_proc_fops);
+        if (!drbd_proc) {
+                printk(KERN_ERR "drbd: unable to register proc file\n");
+                goto Enomem;
+        }
+
+        rwlock_init(&global_state_lock);
+
+        printk(KERN_INFO "drbd: initialized. "
+               "Version: " REL_VERSION " (api:%d/proto:%d-%d)\n",
+               API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX);
+        printk(KERN_INFO "drbd: %s\n", drbd_buildtag());
+        printk(KERN_INFO "drbd: registered as block device major %d\n",
+                DRBD_MAJOR);
+        printk(KERN_INFO "drbd: minor_table @ 0x%p\n", minor_table);
+
+        return 0; /* Success! */
+
+Enomem:
+        drbd_cleanup();
+        if (err == -ENOMEM)
+                /* currently always the case */
+                printk(KERN_ERR "drbd: ran out of memory\n");
+        else
+                printk(KERN_ERR "drbd: initialization failure\n");
+        return err;
+}
+
+void drbd_free_bc(struct drbd_backing_dev *ldev)
+{
+        if (ldev == NULL)
+                return;
+
+        bd_release(ldev->backing_bdev);
+        bd_release(ldev->md_bdev);
+
+        fput(ldev->lo_file);
+        fput(ldev->md_file);
+
+        kfree(ldev);
+}
+
+void drbd_free_sock(struct drbd_conf *mdev)
+{
+        if (mdev->data.socket) {
+                kernel_sock_shutdown(mdev->data.socket, SHUT_RDWR);
+                sock_release(mdev->data.socket);
+                mdev->data.socket = NULL;
+        }
+        if (mdev->meta.socket) {
+                kernel_sock_shutdown(mdev->meta.socket, SHUT_RDWR);
+                sock_release(mdev->meta.socket);
+                mdev->meta.socket = NULL;
+        }
+}
+
+
+void drbd_free_resources(struct drbd_conf *mdev)
+{
+        crypto_free_hash(mdev->csums_tfm);
+        mdev->csums_tfm = NULL;
+        crypto_free_hash(mdev->verify_tfm);
+        mdev->verify_tfm = NULL;
+        crypto_free_hash(mdev->cram_hmac_tfm);
+        mdev->cram_hmac_tfm = NULL;
+        crypto_free_hash(mdev->integrity_w_tfm);
+        mdev->integrity_w_tfm = NULL;
+        crypto_free_hash(mdev->integrity_r_tfm);
+        mdev->integrity_r_tfm = NULL;
+
+        drbd_free_sock(mdev);
+
+        __no_warn(local,
+                  drbd_free_bc(mdev->ldev);
+                  mdev->ldev = NULL;);
+}
+
+/* meta data management */
+
+struct meta_data_on_disk {
+        u64 la_size;           /* last agreed size. */
+        u64 uuid[UI_SIZE];   /* UUIDs. */
+        u64 device_uuid;
+        u64 reserved_u64_1;
+        u32 flags;             /* MDF */
+        u32 magic;
+        u32 md_size_sect;
+        u32 al_offset;         /* offset to this block */
+        u32 al_nr_extents;     /* important for restoring the AL */
+              /* `-- act_log->nr_elements <-- sync_conf.al_extents */
+        u32 bm_offset;         /* offset to the bitmap, from here */
+        u32 bm_bytes_per_bit;  /* BM_BLOCK_SIZE */
+        u32 reserved_u32[4];
+
+} __packed;
+
+/**
+ * drbd_md_sync() - Writes the meta data super block if the MD_DIRTY flag bit is set
+ * @mdev:       DRBD device.
+ */
+void drbd_md_sync(struct drbd_conf *mdev)
+{
+        struct meta_data_on_disk *buffer;
+        sector_t sector;
+        int i;
+
+        if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
+                return;
+        del_timer(&mdev->md_sync_timer);
+
+        /* We use here D_FAILED and not D_ATTACHING because we try to write
+         * metadata even if we detach due to a disk failure! */
+        if (!get_ldev_if_state(mdev, D_FAILED))
+                return;
+
+        trace_drbd_md_io(mdev, WRITE, mdev->ldev);
+
+        mutex_lock(&mdev->md_io_mutex);
+        buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+        memset(buffer, 0, 512);
+
+        buffer->la_size = cpu_to_be64(drbd_get_capacity(mdev->this_bdev));
+        for (i = UI_CURRENT; i < UI_SIZE; i++)
+                buffer->uuid[i] = cpu_to_be64(mdev->ldev->md.uuid[i]);
+        buffer->flags = cpu_to_be32(mdev->ldev->md.flags);
+        buffer->magic = cpu_to_be32(DRBD_MD_MAGIC);
+
+        buffer->md_size_sect  = cpu_to_be32(mdev->ldev->md.md_size_sect);
+        buffer->al_offset     = cpu_to_be32(mdev->ldev->md.al_offset);
+        buffer->al_nr_extents = cpu_to_be32(mdev->act_log->nr_elements);
+        buffer->bm_bytes_per_bit = cpu_to_be32(BM_BLOCK_SIZE);
+        buffer->device_uuid = cpu_to_be64(mdev->ldev->md.device_uuid);
+
+        buffer->bm_offset = cpu_to_be32(mdev->ldev->md.bm_offset);
+
+        D_ASSERT(drbd_md_ss__(mdev, mdev->ldev) == mdev->ldev->md.md_offset);
+        sector = mdev->ldev->md.md_offset;
+
+        if (drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
+                clear_bit(MD_DIRTY, &mdev->flags);
+        } else {
+                /* this was a try anyways ... */
+                dev_err(DEV, "meta data update failed!\n");
+
+                drbd_chk_io_error(mdev, 1, TRUE);
+        }
+
+        /* Update mdev->ldev->md.la_size_sect,
+         * since we updated it on metadata. */
+        mdev->ldev->md.la_size_sect = drbd_get_capacity(mdev->this_bdev);
+
+        mutex_unlock(&mdev->md_io_mutex);
+        put_ldev(mdev);
+}
+
+/**
+ * drbd_md_read() - Reads in the meta data super block
+ * @mdev:       DRBD device.
+ * @bdev:       Device from which the meta data should be read in.
+ *
+ * Return 0 (NO_ERROR) on success, and an enum drbd_ret_codes in case
+ * something goes wrong.  Currently only: ERR_IO_MD_DISK, ERR_MD_INVALID.
+ */
+int drbd_md_read(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+        struct meta_data_on_disk *buffer;
+        int i, rv = NO_ERROR;
+
+        if (!get_ldev_if_state(mdev, D_ATTACHING))
+                return ERR_IO_MD_DISK;
+
+        trace_drbd_md_io(mdev, READ, bdev);
+
+        mutex_lock(&mdev->md_io_mutex);
+        buffer = (struct meta_data_on_disk *)page_address(mdev->md_io_page);
+
+        if (!drbd_md_sync_page_io(mdev, bdev, bdev->md.md_offset, READ)) {
+                /* NOTE: cant do normal error processing here as this is
+                   called BEFORE disk is attached */
+                dev_err(DEV, "Error while reading metadata.\n");
+                rv = ERR_IO_MD_DISK;
+                goto err;
+        }
+
+        if (be32_to_cpu(buffer->magic) != DRBD_MD_MAGIC) {
+                dev_err(DEV, "Error while reading metadata, magic not found.\n");
+                rv = ERR_MD_INVALID;
+                goto err;
+        }
+        if (be32_to_cpu(buffer->al_offset) != bdev->md.al_offset) {
+                dev_err(DEV, "unexpected al_offset: %d (expected %d)\n",
+                    be32_to_cpu(buffer->al_offset), bdev->md.al_offset);
+                rv = ERR_MD_INVALID;
+                goto err;
+        }
+        if (be32_to_cpu(buffer->bm_offset) != bdev->md.bm_offset) {
+                dev_err(DEV, "unexpected bm_offset: %d (expected %d)\n",
+                    be32_to_cpu(buffer->bm_offset), bdev->md.bm_offset);
+                rv = ERR_MD_INVALID;
+                goto err;
+        }
+        if (be32_to_cpu(buffer->md_size_sect) != bdev->md.md_size_sect) {
+                dev_err(DEV, "unexpected md_size: %u (expected %u)\n",
+                    be32_to_cpu(buffer->md_size_sect), bdev->md.md_size_sect);
+                rv = ERR_MD_INVALID;
+                goto err;
+        }
+
+        if (be32_to_cpu(buffer->bm_bytes_per_bit) != BM_BLOCK_SIZE) {
+                dev_err(DEV, "unexpected bm_bytes_per_bit: %u (expected %u)\n",
+                    be32_to_cpu(buffer->bm_bytes_per_bit), BM_BLOCK_SIZE);
+                rv = ERR_MD_INVALID;
+                goto err;
+        }
+
+        bdev->md.la_size_sect = be64_to_cpu(buffer->la_size);
+        for (i = UI_CURRENT; i < UI_SIZE; i++)
+                bdev->md.uuid[i] = be64_to_cpu(buffer->uuid[i]);
+        bdev->md.flags = be32_to_cpu(buffer->flags);
+        mdev->sync_conf.al_extents = be32_to_cpu(buffer->al_nr_extents);
+        bdev->md.device_uuid = be64_to_cpu(buffer->device_uuid);
+
+        if (mdev->sync_conf.al_extents < 7)
+                mdev->sync_conf.al_extents = 127;
+
+ err:
+        mutex_unlock(&mdev->md_io_mutex);
+        put_ldev(mdev);
+
+        return rv;
+}
+
+/**
+ * drbd_md_mark_dirty() - Mark meta data super block as dirty
+ * @mdev:       DRBD device.
+ *
+ * Call this function if you change anything that should be written to
+ * the meta-data super block. This function sets MD_DIRTY, and starts a
+ * timer that ensures that within five seconds you have to call drbd_md_sync().
+ */
+void drbd_md_mark_dirty(struct drbd_conf *mdev)
+{
+        set_bit(MD_DIRTY, &mdev->flags);
+        mod_timer(&mdev->md_sync_timer, jiffies + 5*HZ);
+}
+
+
+static void drbd_uuid_move_history(struct drbd_conf *mdev) __must_hold(local)
+{
+        int i;
+
+        for (i = UI_HISTORY_START; i < UI_HISTORY_END; i++) {
+                mdev->ldev->md.uuid[i+1] = mdev->ldev->md.uuid[i];
+
+                trace_drbd_uuid(mdev, i+1);
+        }
+}
+
+void _drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
+{
+        if (idx == UI_CURRENT) {
+                if (mdev->state.role == R_PRIMARY)
+                        val |= 1;
+                else
+                        val &= ~((u64)1);
+
+                drbd_set_ed_uuid(mdev, val);
+        }
+
+        mdev->ldev->md.uuid[idx] = val;
+        trace_drbd_uuid(mdev, idx);
+        drbd_md_mark_dirty(mdev);
+}
+
+
+void drbd_uuid_set(struct drbd_conf *mdev, int idx, u64 val) __must_hold(local)
+{
+        if (mdev->ldev->md.uuid[idx]) {
+                drbd_uuid_move_history(mdev);
+                mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[idx];
+                trace_drbd_uuid(mdev, UI_HISTORY_START);
+        }
+        _drbd_uuid_set(mdev, idx, val);
+}
+
+/**
+ * drbd_uuid_new_current() - Creates a new current UUID
+ * @mdev:       DRBD device.
+ *
+ * Creates a new current UUID, and rotates the old current UUID into
+ * the bitmap slot. Causes an incremental resync upon next connect.
+ */
+void drbd_uuid_new_current(struct drbd_conf *mdev) __must_hold(local)
+{
+        u64 val;
+
+        dev_info(DEV, "Creating new current UUID\n");
+        D_ASSERT(mdev->ldev->md.uuid[UI_BITMAP] == 0);
+        mdev->ldev->md.uuid[UI_BITMAP] = mdev->ldev->md.uuid[UI_CURRENT];
+        trace_drbd_uuid(mdev, UI_BITMAP);
+
+        get_random_bytes(&val, sizeof(u64));
+        _drbd_uuid_set(mdev, UI_CURRENT, val);
+}
+
+void drbd_uuid_set_bm(struct drbd_conf *mdev, u64 val) __must_hold(local)
+{
+        if (mdev->ldev->md.uuid[UI_BITMAP] == 0 && val == 0)
+                return;
+
+        if (val == 0) {
+                drbd_uuid_move_history(mdev);
+                mdev->ldev->md.uuid[UI_HISTORY_START] = mdev->ldev->md.uuid[UI_BITMAP];
+                mdev->ldev->md.uuid[UI_BITMAP] = 0;
+                trace_drbd_uuid(mdev, UI_HISTORY_START);
+                trace_drbd_uuid(mdev, UI_BITMAP);
+        } else {
+                if (mdev->ldev->md.uuid[UI_BITMAP])
+                        dev_warn(DEV, "bm UUID already set");
+
+                mdev->ldev->md.uuid[UI_BITMAP] = val;
+                mdev->ldev->md.uuid[UI_BITMAP] &= ~((u64)1);
+
+                trace_drbd_uuid(mdev, UI_BITMAP);
+        }
+        drbd_md_mark_dirty(mdev);
+}
+
+/**
+ * drbd_bmio_set_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
+ * @mdev:       DRBD device.
+ *
+ * Sets all bits in the bitmap and writes the whole bitmap to stable storage.
+ */
+int drbd_bmio_set_n_write(struct drbd_conf *mdev)
+{
+        int rv = -EIO;
+
+        if (get_ldev_if_state(mdev, D_ATTACHING)) {
+                drbd_md_set_flag(mdev, MDF_FULL_SYNC);
+                drbd_md_sync(mdev);
+                drbd_bm_set_all(mdev);
+
+                rv = drbd_bm_write(mdev);
+
+                if (!rv) {
+                        drbd_md_clear_flag(mdev, MDF_FULL_SYNC);
+                        drbd_md_sync(mdev);
+                }
+
+                put_ldev(mdev);
+        }
+
+        return rv;
+}
+
+/**
+ * drbd_bmio_clear_n_write() - io_fn for drbd_queue_bitmap_io() or drbd_bitmap_io()
+ * @mdev:       DRBD device.
+ *
+ * Clears all bits in the bitmap and writes the whole bitmap to stable storage.
+ */
+int drbd_bmio_clear_n_write(struct drbd_conf *mdev)
+{
+        int rv = -EIO;
+
+        if (get_ldev_if_state(mdev, D_ATTACHING)) {
+                drbd_bm_clear_all(mdev);
+                rv = drbd_bm_write(mdev);
+                put_ldev(mdev);
+        }
+
+        return rv;
+}
+
+static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct bm_io_work *work = container_of(w, struct bm_io_work, w);
+        int rv;
+
+        D_ASSERT(atomic_read(&mdev->ap_bio_cnt) == 0);
+
+        drbd_bm_lock(mdev, work->why);
+        rv = work->io_fn(mdev);
+        drbd_bm_unlock(mdev);
+
+        clear_bit(BITMAP_IO, &mdev->flags);
+        wake_up(&mdev->misc_wait);
+
+        if (work->done)
+                work->done(mdev, rv);
+
+        clear_bit(BITMAP_IO_QUEUED, &mdev->flags);
+        work->why = NULL;
+
+        return 1;
+}
+
+/**
+ * drbd_queue_bitmap_io() - Queues an IO operation on the whole bitmap
+ * @mdev:       DRBD device.
+ * @io_fn:      IO callback to be called when bitmap IO is possible
+ * @done:       callback to be called after the bitmap IO was performed
+ * @why:        Descriptive text of the reason for doing the IO
+ *
+ * While IO on the bitmap happens we freeze application IO thus we ensure
+ * that drbd_set_out_of_sync() can not be called. This function MAY ONLY be
+ * called from worker context. It MUST NOT be used while a previous such
+ * work is still pending!
+ */
+void drbd_queue_bitmap_io(struct drbd_conf *mdev,
+                          int (*io_fn)(struct drbd_conf *),
+                          void (*done)(struct drbd_conf *, int),
+                          char *why)
+{
+        D_ASSERT(current == mdev->worker.task);
+
+        D_ASSERT(!test_bit(BITMAP_IO_QUEUED, &mdev->flags));
+        D_ASSERT(!test_bit(BITMAP_IO, &mdev->flags));
+        D_ASSERT(list_empty(&mdev->bm_io_work.w.list));
+        if (mdev->bm_io_work.why)
+                dev_err(DEV, "FIXME going to queue '%s' but '%s' still pending?\n",
+                        why, mdev->bm_io_work.why);
+
+        mdev->bm_io_work.io_fn = io_fn;
+        mdev->bm_io_work.done = done;
+        mdev->bm_io_work.why = why;
+
+        set_bit(BITMAP_IO, &mdev->flags);
+        if (atomic_read(&mdev->ap_bio_cnt) == 0) {
+                if (list_empty(&mdev->bm_io_work.w.list)) {
+                        set_bit(BITMAP_IO_QUEUED, &mdev->flags);
+                        drbd_queue_work(&mdev->data.work, &mdev->bm_io_work.w);
+                } else
+                        dev_err(DEV, "FIXME avoided double queuing bm_io_work\n");
+        }
+}
+
+/**
+ * drbd_bitmap_io() -  Does an IO operation on the whole bitmap
+ * @mdev:       DRBD device.
+ * @io_fn:      IO callback to be called when bitmap IO is possible
+ * @why:        Descriptive text of the reason for doing the IO
+ *
+ * freezes application IO while that the actual IO operations runs. This
+ * functions MAY NOT be called from worker context.
+ */
+int drbd_bitmap_io(struct drbd_conf *mdev, int (*io_fn)(struct drbd_conf *), char *why)
+{
+        int rv;
+
+        D_ASSERT(current != mdev->worker.task);
+
+        drbd_suspend_io(mdev);
+
+        drbd_bm_lock(mdev, why);
+        rv = io_fn(mdev);
+        drbd_bm_unlock(mdev);
+
+        drbd_resume_io(mdev);
+
+        return rv;
+}
+
+void drbd_md_set_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
+{
+        if ((mdev->ldev->md.flags & flag) != flag) {
+                drbd_md_mark_dirty(mdev);
+                mdev->ldev->md.flags |= flag;
+        }
+}
+
+void drbd_md_clear_flag(struct drbd_conf *mdev, int flag) __must_hold(local)
+{
+        if ((mdev->ldev->md.flags & flag) != 0) {
+                drbd_md_mark_dirty(mdev);
+                mdev->ldev->md.flags &= ~flag;
+        }
+}
+int drbd_md_test_flag(struct drbd_backing_dev *bdev, int flag)
+{
+        return (bdev->md.flags & flag) != 0;
+}
+
+static void md_sync_timer_fn(unsigned long data)
+{
+        struct drbd_conf *mdev = (struct drbd_conf *) data;
+
+        drbd_queue_work_front(&mdev->data.work, &mdev->md_sync_work);
+}
+
+static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        dev_warn(DEV, "md_sync_timer expired! Worker calls drbd_md_sync().\n");
+        drbd_md_sync(mdev);
+
+        return 1;
+}
+
+#ifdef CONFIG_DRBD_FAULT_INJECTION
+/* Fault insertion support including random number generator shamelessly
+ * stolen from kernel/rcutorture.c */
+struct fault_random_state {
+        unsigned long state;
+        unsigned long count;
+};
+
+#define FAULT_RANDOM_MULT 39916801  /* prime */
+#define FAULT_RANDOM_ADD        479001701 /* prime */
+#define FAULT_RANDOM_REFRESH 10000
+
+/*
+ * Crude but fast random-number generator.  Uses a linear congruential
+ * generator, with occasional help from get_random_bytes().
+ */
+static unsigned long
+_drbd_fault_random(struct fault_random_state *rsp)
+{
+        long refresh;
+
+        if (--rsp->count < 0) {
+                get_random_bytes(&refresh, sizeof(refresh));
+                rsp->state += refresh;
+                rsp->count = FAULT_RANDOM_REFRESH;
+        }
+        rsp->state = rsp->state * FAULT_RANDOM_MULT + FAULT_RANDOM_ADD;
+        return swahw32(rsp->state);
+}
+
+static char *
+_drbd_fault_str(unsigned int type) {
+        static char *_faults[] = {
+                [DRBD_FAULT_MD_WR] = "Meta-data write",
+                [DRBD_FAULT_MD_RD] = "Meta-data read",
+                [DRBD_FAULT_RS_WR] = "Resync write",
+                [DRBD_FAULT_RS_RD] = "Resync read",
+                [DRBD_FAULT_DT_WR] = "Data write",
+                [DRBD_FAULT_DT_RD] = "Data read",
+                [DRBD_FAULT_DT_RA] = "Data read ahead",
+                [DRBD_FAULT_BM_ALLOC] = "BM allocation",
+                [DRBD_FAULT_AL_EE] = "EE allocation"
+        };
+
+        return (type < DRBD_FAULT_MAX) ? _faults[type] : "**Unknown**";
+}
+
+unsigned int
+_drbd_insert_fault(struct drbd_conf *mdev, unsigned int type)
+{
+        static struct fault_random_state rrs = {0, 0};
+
+        unsigned int ret = (
+                (fault_devs == 0 ||
+                        ((1 << mdev_to_minor(mdev)) & fault_devs) != 0) &&
+                (((_drbd_fault_random(&rrs) % 100) + 1) <= fault_rate));
+
+        if (ret) {
+                fault_count++;
+
+                if (printk_ratelimit())
+                        dev_warn(DEV, "***Simulating %s failure\n",
+                                _drbd_fault_str(type));
+        }
+
+        return ret;
+}
+#endif
+
+const char *drbd_buildtag(void)
+{
+        /* DRBD built from external sources has here a reference to the
+           git hash of the source code. */
+
+        static char buildtag[38] = "\0uilt-in";
+
+        if (buildtag[0] == 0) {
+#ifdef CONFIG_MODULES
+                if (THIS_MODULE != NULL)
+                        sprintf(buildtag, "srcversion: %-24s", THIS_MODULE->srcversion);
+                else
+#endif
+                        buildtag[0] = 'b';
+        }
+
+        return buildtag;
+}
+
+module_init(drbd_init)
+module_exit(drbd_cleanup)
+
+/* For drbd_tracing: */
+EXPORT_SYMBOL(drbd_conn_str);
+EXPORT_SYMBOL(drbd_role_str);
+EXPORT_SYMBOL(drbd_disk_str);
+EXPORT_SYMBOL(drbd_set_st_err_str);
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
new file mode 100644
index 000000000000..1927acefe230
--- /dev/null
+++ b/drivers/block/drbd/drbd_nl.c
@@ -0,0 +1,2365 @@
+/*
+   drbd_nl.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/drbd.h>
+#include <linux/in.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/connector.h>
+#include <linux/blkpg.h>
+#include <linux/cpumask.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_wrappers.h"
+#include <asm/unaligned.h>
+#include <linux/drbd_tag_magic.h>
+#include <linux/drbd_limits.h>
+
+static unsigned short *tl_add_blob(unsigned short *, enum drbd_tags, const void *, int);
+static unsigned short *tl_add_str(unsigned short *, enum drbd_tags, const char *);
+static unsigned short *tl_add_int(unsigned short *, enum drbd_tags, const void *);
+
+/* see get_sb_bdev and bd_claim */
+static char *drbd_m_holder = "Hands off! this is DRBD's meta data device.";
+
+/* Generate the tag_list to struct functions */
+#define NL_PACKET(name, number, fields) \
+static int name ## _from_tags(struct drbd_conf *mdev, \
+        unsigned short *tags, struct name *arg) __attribute__ ((unused)); \
+static int name ## _from_tags(struct drbd_conf *mdev, \
+        unsigned short *tags, struct name *arg) \
+{ \
+        int tag; \
+        int dlen; \
+        \
+        while ((tag = get_unaligned(tags++)) != TT_END) {       \
+                dlen = get_unaligned(tags++);                   \
+                switch (tag_number(tag)) { \
+                fields \
+                default: \
+                        if (tag & T_MANDATORY) { \
+                                dev_err(DEV, "Unknown tag: %d\n", tag_number(tag)); \
+                                return 0; \
+                        } \
+                } \
+                tags = (unsigned short *)((char *)tags + dlen); \
+        } \
+        return 1; \
+}
+#define NL_INTEGER(pn, pr, member) \
+        case pn: /* D_ASSERT( tag_type(tag) == TT_INTEGER ); */ \
+                arg->member = get_unaligned((int *)(tags));     \
+                break;
+#define NL_INT64(pn, pr, member) \
+        case pn: /* D_ASSERT( tag_type(tag) == TT_INT64 ); */ \
+                arg->member = get_unaligned((u64 *)(tags));     \
+                break;
+#define NL_BIT(pn, pr, member) \
+        case pn: /* D_ASSERT( tag_type(tag) == TT_BIT ); */ \
+                arg->member = *(char *)(tags) ? 1 : 0; \
+                break;
+#define NL_STRING(pn, pr, member, len) \
+        case pn: /* D_ASSERT( tag_type(tag) == TT_STRING ); */ \
+                if (dlen > len) { \
+                        dev_err(DEV, "arg too long: %s (%u wanted, max len: %u bytes)\n", \
+                                #member, dlen, (unsigned int)len); \
+                        return 0; \
+                } \
+                 arg->member ## _len = dlen; \
+                 memcpy(arg->member, tags, min_t(size_t, dlen, len)); \
+                 break;
+#include "linux/drbd_nl.h"
+
+/* Generate the struct to tag_list functions */
+#define NL_PACKET(name, number, fields) \
+static unsigned short* \
+name ## _to_tags(struct drbd_conf *mdev, \
+        struct name *arg, unsigned short *tags) __attribute__ ((unused)); \
+static unsigned short* \
+name ## _to_tags(struct drbd_conf *mdev, \
+        struct name *arg, unsigned short *tags) \
+{ \
+        fields \
+        return tags; \
+}
+
+#define NL_INTEGER(pn, pr, member) \
+        put_unaligned(pn | pr | TT_INTEGER, tags++);    \
+        put_unaligned(sizeof(int), tags++);             \
+        put_unaligned(arg->member, (int *)tags);        \
+        tags = (unsigned short *)((char *)tags+sizeof(int));
+#define NL_INT64(pn, pr, member) \
+        put_unaligned(pn | pr | TT_INT64, tags++);      \
+        put_unaligned(sizeof(u64), tags++);             \
+        put_unaligned(arg->member, (u64 *)tags);        \
+        tags = (unsigned short *)((char *)tags+sizeof(u64));
+#define NL_BIT(pn, pr, member) \
+        put_unaligned(pn | pr | TT_BIT, tags++);        \
+        put_unaligned(sizeof(char), tags++);            \
+        *(char *)tags = arg->member; \
+        tags = (unsigned short *)((char *)tags+sizeof(char));
+#define NL_STRING(pn, pr, member, len) \
+        put_unaligned(pn | pr | TT_STRING, tags++);     \
+        put_unaligned(arg->member ## _len, tags++);     \
+        memcpy(tags, arg->member, arg->member ## _len); \
+        tags = (unsigned short *)((char *)tags + arg->member ## _len);
+#include "linux/drbd_nl.h"
+
+void drbd_bcast_ev_helper(struct drbd_conf *mdev, char *helper_name);
+void drbd_nl_send_reply(struct cn_msg *, int);
+
+int drbd_khelper(struct drbd_conf *mdev, char *cmd)
+{
+        char *envp[] = { "HOME=/",
+                        "TERM=linux",
+                        "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
+                        NULL, /* Will be set to address family */
+                        NULL, /* Will be set to address */
+                        NULL };
+
+        char mb[12], af[20], ad[60], *afs;
+        char *argv[] = {usermode_helper, cmd, mb, NULL };
+        int ret;
+
+        snprintf(mb, 12, "minor-%d", mdev_to_minor(mdev));
+
+        if (get_net_conf(mdev)) {
+                switch (((struct sockaddr *)mdev->net_conf->peer_addr)->sa_family) {
+                case AF_INET6:
+                        afs = "ipv6";
+                        snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI6",
+                                 &((struct sockaddr_in6 *)mdev->net_conf->peer_addr)->sin6_addr);
+                        break;
+                case AF_INET:
+                        afs = "ipv4";
+                        snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI4",
+                                 &((struct sockaddr_in *)mdev->net_conf->peer_addr)->sin_addr);
+                        break;
+                default:
+                        afs = "ssocks";
+                        snprintf(ad, 60, "DRBD_PEER_ADDRESS=%pI4",
+                                 &((struct sockaddr_in *)mdev->net_conf->peer_addr)->sin_addr);
+                }
+                snprintf(af, 20, "DRBD_PEER_AF=%s", afs);
+                envp[3]=af;
+                envp[4]=ad;
+                put_net_conf(mdev);
+        }
+
+        dev_info(DEV, "helper command: %s %s %s\n", usermode_helper, cmd, mb);
+
+        drbd_bcast_ev_helper(mdev, cmd);
+        ret = call_usermodehelper(usermode_helper, argv, envp, 1);
+        if (ret)
+                dev_warn(DEV, "helper command: %s %s %s exit code %u (0x%x)\n",
+                                usermode_helper, cmd, mb,
+                                (ret >> 8) & 0xff, ret);
+        else
+                dev_info(DEV, "helper command: %s %s %s exit code %u (0x%x)\n",
+                                usermode_helper, cmd, mb,
+                                (ret >> 8) & 0xff, ret);
+
+        if (ret < 0) /* Ignore any ERRNOs we got. */
+                ret = 0;
+
+        return ret;
+}
+
+enum drbd_disk_state drbd_try_outdate_peer(struct drbd_conf *mdev)
+{
+        char *ex_to_string;
+        int r;
+        enum drbd_disk_state nps;
+        enum drbd_fencing_p fp;
+
+        D_ASSERT(mdev->state.pdsk == D_UNKNOWN);
+
+        if (get_ldev_if_state(mdev, D_CONSISTENT)) {
+                fp = mdev->ldev->dc.fencing;
+                put_ldev(mdev);
+        } else {
+                dev_warn(DEV, "Not fencing peer, I'm not even Consistent myself.\n");
+                return mdev->state.pdsk;
+        }
+
+        if (fp == FP_STONITH)
+                _drbd_request_state(mdev, NS(susp, 1), CS_WAIT_COMPLETE);
+
+        r = drbd_khelper(mdev, "fence-peer");
+
+        switch ((r>>8) & 0xff) {
+        case 3: /* peer is inconsistent */
+                ex_to_string = "peer is inconsistent or worse";
+                nps = D_INCONSISTENT;
+                break;
+        case 4: /* peer got outdated, or was already outdated */
+                ex_to_string = "peer was fenced";
+                nps = D_OUTDATED;
+                break;
+        case 5: /* peer was down */
+                if (mdev->state.disk == D_UP_TO_DATE) {
+                        /* we will(have) create(d) a new UUID anyways... */
+                        ex_to_string = "peer is unreachable, assumed to be dead";
+                        nps = D_OUTDATED;
+                } else {
+                        ex_to_string = "peer unreachable, doing nothing since disk != UpToDate";
+                        nps = mdev->state.pdsk;
+                }
+                break;
+        case 6: /* Peer is primary, voluntarily outdate myself.
+                 * This is useful when an unconnected R_SECONDARY is asked to
+                 * become R_PRIMARY, but finds the other peer being active. */
+                ex_to_string = "peer is active";
+                dev_warn(DEV, "Peer is primary, outdating myself.\n");
+                nps = D_UNKNOWN;
+                _drbd_request_state(mdev, NS(disk, D_OUTDATED), CS_WAIT_COMPLETE);
+                break;
+        case 7:
+                if (fp != FP_STONITH)
+                        dev_err(DEV, "fence-peer() = 7 && fencing != Stonith !!!\n");
+                ex_to_string = "peer was stonithed";
+                nps = D_OUTDATED;
+                break;
+        default:
+                /* The script is broken ... */
+                nps = D_UNKNOWN;
+                dev_err(DEV, "fence-peer helper broken, returned %d\n", (r>>8)&0xff);
+                return nps;
+        }
+
+        dev_info(DEV, "fence-peer helper returned %d (%s)\n",
+                        (r>>8) & 0xff, ex_to_string);
+        return nps;
+}
+
+
+int drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
+{
+        const int max_tries = 4;
+        int r = 0;
+        int try = 0;
+        int forced = 0;
+        union drbd_state mask, val;
+        enum drbd_disk_state nps;
+
+        if (new_role == R_PRIMARY)
+                request_ping(mdev); /* Detect a dead peer ASAP */
+
+        mutex_lock(&mdev->state_mutex);
+
+        mask.i = 0; mask.role = R_MASK;
+        val.i  = 0; val.role  = new_role;
+
+        while (try++ < max_tries) {
+                r = _drbd_request_state(mdev, mask, val, CS_WAIT_COMPLETE);
+
+                /* in case we first succeeded to outdate,
+                 * but now suddenly could establish a connection */
+                if (r == SS_CW_FAILED_BY_PEER && mask.pdsk != 0) {
+                        val.pdsk = 0;
+                        mask.pdsk = 0;
+                        continue;
+                }
+
+                if (r == SS_NO_UP_TO_DATE_DISK && force &&
+                    (mdev->state.disk == D_INCONSISTENT ||
+                     mdev->state.disk == D_OUTDATED)) {
+                        mask.disk = D_MASK;
+                        val.disk  = D_UP_TO_DATE;
+                        forced = 1;
+                        continue;
+                }
+
+                if (r == SS_NO_UP_TO_DATE_DISK &&
+                    mdev->state.disk == D_CONSISTENT && mask.pdsk == 0) {
+                        D_ASSERT(mdev->state.pdsk == D_UNKNOWN);
+                        nps = drbd_try_outdate_peer(mdev);
+
+                        if (nps == D_OUTDATED || nps == D_INCONSISTENT) {
+                                val.disk = D_UP_TO_DATE;
+                                mask.disk = D_MASK;
+                        }
+
+                        val.pdsk = nps;
+                        mask.pdsk = D_MASK;
+
+                        continue;
+                }
+
+                if (r == SS_NOTHING_TO_DO)
+                        goto fail;
+                if (r == SS_PRIMARY_NOP && mask.pdsk == 0) {
+                        nps = drbd_try_outdate_peer(mdev);
+
+                        if (force && nps > D_OUTDATED) {
+                                dev_warn(DEV, "Forced into split brain situation!\n");
+                                nps = D_OUTDATED;
+                        }
+
+                        mask.pdsk = D_MASK;
+                        val.pdsk  = nps;
+
+                        continue;
+                }
+                if (r == SS_TWO_PRIMARIES) {
+                        /* Maybe the peer is detected as dead very soon...
+                           retry at most once more in this case. */
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout((mdev->net_conf->ping_timeo+1)*HZ/10);
+                        if (try < max_tries)
+                                try = max_tries - 1;
+                        continue;
+                }
+                if (r < SS_SUCCESS) {
+                        r = _drbd_request_state(mdev, mask, val,
+                                                CS_VERBOSE + CS_WAIT_COMPLETE);
+                        if (r < SS_SUCCESS)
+                                goto fail;
+                }
+                break;
+        }
+
+        if (r < SS_SUCCESS)
+                goto fail;
+
+        if (forced)
+                dev_warn(DEV, "Forced to consider local data as UpToDate!\n");
+
+        /* Wait until nothing is on the fly :) */
+        wait_event(mdev->misc_wait, atomic_read(&mdev->ap_pending_cnt) == 0);
+
+        if (new_role == R_SECONDARY) {
+                set_disk_ro(mdev->vdisk, TRUE);
+                if (get_ldev(mdev)) {
+                        mdev->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
+                        put_ldev(mdev);
+                }
+        } else {
+                if (get_net_conf(mdev)) {
+                        mdev->net_conf->want_lose = 0;
+                        put_net_conf(mdev);
+                }
+                set_disk_ro(mdev->vdisk, FALSE);
+                if (get_ldev(mdev)) {
+                        if (((mdev->state.conn < C_CONNECTED ||
+                               mdev->state.pdsk <= D_FAILED)
+                              && mdev->ldev->md.uuid[UI_BITMAP] == 0) || forced)
+                                drbd_uuid_new_current(mdev);
+
+                        mdev->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
+                        put_ldev(mdev);
+                }
+        }
+
+        if ((new_role == R_SECONDARY) && get_ldev(mdev)) {
+                drbd_al_to_on_disk_bm(mdev);
+                put_ldev(mdev);
+        }
+
+        if (mdev->state.conn >= C_WF_REPORT_PARAMS) {
+                /* if this was forced, we should consider sync */
+                if (forced)
+                        drbd_send_uuids(mdev);
+                drbd_send_state(mdev);
+        }
+
+        drbd_md_sync(mdev);
+
+        kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+ fail:
+        mutex_unlock(&mdev->state_mutex);
+        return r;
+}
+
+
+static int drbd_nl_primary(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                           struct drbd_nl_cfg_reply *reply)
+{
+        struct primary primary_args;
+
+        memset(&primary_args, 0, sizeof(struct primary));
+        if (!primary_from_tags(mdev, nlp->tag_list, &primary_args)) {
+                reply->ret_code = ERR_MANDATORY_TAG;
+                return 0;
+        }
+
+        reply->ret_code =
+                drbd_set_role(mdev, R_PRIMARY, primary_args.overwrite_peer);
+
+        return 0;
+}
+
+static int drbd_nl_secondary(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                             struct drbd_nl_cfg_reply *reply)
+{
+        reply->ret_code = drbd_set_role(mdev, R_SECONDARY, 0);
+
+        return 0;
+}
+
+/* initializes the md.*_offset members, so we are able to find
+ * the on disk meta data */
+static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
+                                       struct drbd_backing_dev *bdev)
+{
+        sector_t md_size_sect = 0;
+        switch (bdev->dc.meta_dev_idx) {
+        default:
+                /* v07 style fixed size indexed meta data */
+                bdev->md.md_size_sect = MD_RESERVED_SECT;
+                bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
+                bdev->md.al_offset = MD_AL_OFFSET;
+                bdev->md.bm_offset = MD_BM_OFFSET;
+                break;
+        case DRBD_MD_INDEX_FLEX_EXT:
+                /* just occupy the full device; unit: sectors */
+                bdev->md.md_size_sect = drbd_get_capacity(bdev->md_bdev);
+                bdev->md.md_offset = 0;
+                bdev->md.al_offset = MD_AL_OFFSET;
+                bdev->md.bm_offset = MD_BM_OFFSET;
+                break;
+        case DRBD_MD_INDEX_INTERNAL:
+        case DRBD_MD_INDEX_FLEX_INT:
+                bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
+                /* al size is still fixed */
+                bdev->md.al_offset = -MD_AL_MAX_SIZE;
+                /* we need (slightly less than) ~ this much bitmap sectors: */
+                md_size_sect = drbd_get_capacity(bdev->backing_bdev);
+                md_size_sect = ALIGN(md_size_sect, BM_SECT_PER_EXT);
+                md_size_sect = BM_SECT_TO_EXT(md_size_sect);
+                md_size_sect = ALIGN(md_size_sect, 8);
+
+                /* plus the "drbd meta data super block",
+                 * and the activity log; */
+                md_size_sect += MD_BM_OFFSET;
+
+                bdev->md.md_size_sect = md_size_sect;
+                /* bitmap offset is adjusted by 'super' block size */
+                bdev->md.bm_offset   = -md_size_sect + MD_AL_OFFSET;
+                break;
+        }
+}
+
+char *ppsize(char *buf, unsigned long long size)
+{
+        /* Needs 9 bytes at max. */
+        static char units[] = { 'K', 'M', 'G', 'T', 'P', 'E' };
+        int base = 0;
+        while (size >= 10000) {
+                /* shift + round */
+                size = (size >> 10) + !!(size & (1<<9));
+                base++;
+        }
+        sprintf(buf, "%lu %cB", (long)size, units[base]);
+
+        return buf;
+}
+
+/* there is still a theoretical deadlock when called from receiver
+ * on an D_INCONSISTENT R_PRIMARY:
+ *  remote READ does inc_ap_bio, receiver would need to receive answer
+ *  packet from remote to dec_ap_bio again.
+ *  receiver receive_sizes(), comes here,
+ *  waits for ap_bio_cnt == 0. -> deadlock.
+ * but this cannot happen, actually, because:
+ *  R_PRIMARY D_INCONSISTENT, and peer's disk is unreachable
+ *  (not connected, or bad/no disk on peer):
+ *  see drbd_fail_request_early, ap_bio_cnt is zero.
+ *  R_PRIMARY D_INCONSISTENT, and C_SYNC_TARGET:
+ *  peer may not initiate a resize.
+ */
+void drbd_suspend_io(struct drbd_conf *mdev)
+{
+        set_bit(SUSPEND_IO, &mdev->flags);
+        wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
+}
+
+void drbd_resume_io(struct drbd_conf *mdev)
+{
+        clear_bit(SUSPEND_IO, &mdev->flags);
+        wake_up(&mdev->misc_wait);
+}
+
+/**
+ * drbd_determine_dev_size() -  Sets the right device size obeying all constraints
+ * @mdev:       DRBD device.
+ *
+ * Returns 0 on success, negative return values indicate errors.
+ * You should call drbd_md_sync() after calling this function.
+ */
+enum determine_dev_size drbd_determin_dev_size(struct drbd_conf *mdev) __must_hold(local)
+{
+        sector_t prev_first_sect, prev_size; /* previous meta location */
+        sector_t la_size;
+        sector_t size;
+        char ppb[10];
+
+        int md_moved, la_size_changed;
+        enum determine_dev_size rv = unchanged;
+
+        /* race:
+         * application request passes inc_ap_bio,
+         * but then cannot get an AL-reference.
+         * this function later may wait on ap_bio_cnt == 0. -> deadlock.
+         *
+         * to avoid that:
+         * Suspend IO right here.
+         * still lock the act_log to not trigger ASSERTs there.
+         */
+        drbd_suspend_io(mdev);
+
+        /* no wait necessary anymore, actually we could assert that */
+        wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+
+        prev_first_sect = drbd_md_first_sector(mdev->ldev);
+        prev_size = mdev->ldev->md.md_size_sect;
+        la_size = mdev->ldev->md.la_size_sect;
+
+        /* TODO: should only be some assert here, not (re)init... */
+        drbd_md_set_sector_offsets(mdev, mdev->ldev);
+
+        size = drbd_new_dev_size(mdev, mdev->ldev);
+
+        if (drbd_get_capacity(mdev->this_bdev) != size ||
+            drbd_bm_capacity(mdev) != size) {
+                int err;
+                err = drbd_bm_resize(mdev, size);
+                if (unlikely(err)) {
+                        /* currently there is only one error: ENOMEM! */
+                        size = drbd_bm_capacity(mdev)>>1;
+                        if (size == 0) {
+                                dev_err(DEV, "OUT OF MEMORY! "
+                                    "Could not allocate bitmap!\n");
+                        } else {
+                                dev_err(DEV, "BM resizing failed. "
+                                    "Leaving size unchanged at size = %lu KB\n",
+                                    (unsigned long)size);
+                        }
+                        rv = dev_size_error;
+                }
+                /* racy, see comments above. */
+                drbd_set_my_capacity(mdev, size);
+                mdev->ldev->md.la_size_sect = size;
+                dev_info(DEV, "size = %s (%llu KB)\n", ppsize(ppb, size>>1),
+                     (unsigned long long)size>>1);
+        }
+        if (rv == dev_size_error)
+                goto out;
+
+        la_size_changed = (la_size != mdev->ldev->md.la_size_sect);
+
+        md_moved = prev_first_sect != drbd_md_first_sector(mdev->ldev)
+                || prev_size       != mdev->ldev->md.md_size_sect;
+
+        if (la_size_changed || md_moved) {
+                drbd_al_shrink(mdev); /* All extents inactive. */
+                dev_info(DEV, "Writing the whole bitmap, %s\n",
+                         la_size_changed && md_moved ? "size changed and md moved" :
+                         la_size_changed ? "size changed" : "md moved");
+                rv = drbd_bitmap_io(mdev, &drbd_bm_write, "size changed"); /* does drbd_resume_io() ! */
+                drbd_md_mark_dirty(mdev);
+        }
+
+        if (size > la_size)
+                rv = grew;
+        if (size < la_size)
+                rv = shrunk;
+out:
+        lc_unlock(mdev->act_log);
+        wake_up(&mdev->al_wait);
+        drbd_resume_io(mdev);
+
+        return rv;
+}
+
+sector_t
+drbd_new_dev_size(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
+{
+        sector_t p_size = mdev->p_size;   /* partner's disk size. */
+        sector_t la_size = bdev->md.la_size_sect; /* last agreed size. */
+        sector_t m_size; /* my size */
+        sector_t u_size = bdev->dc.disk_size; /* size requested by user. */
+        sector_t size = 0;
+
+        m_size = drbd_get_max_capacity(bdev);
+
+        if (p_size && m_size) {
+                size = min_t(sector_t, p_size, m_size);
+        } else {
+                if (la_size) {
+                        size = la_size;
+                        if (m_size && m_size < size)
+                                size = m_size;
+                        if (p_size && p_size < size)
+                                size = p_size;
+                } else {
+                        if (m_size)
+                                size = m_size;
+                        if (p_size)
+                                size = p_size;
+                }
+        }
+
+        if (size == 0)
+                dev_err(DEV, "Both nodes diskless!\n");
+
+        if (u_size) {
+                if (u_size > size)
+                        dev_err(DEV, "Requested disk size is too big (%lu > %lu)\n",
+                            (unsigned long)u_size>>1, (unsigned long)size>>1);
+                else
+                        size = u_size;
+        }
+
+        return size;
+}
+
+/**
+ * drbd_check_al_size() - Ensures that the AL is of the right size
+ * @mdev:       DRBD device.
+ *
+ * Returns -EBUSY if current al lru is still used, -ENOMEM when allocation
+ * failed, and 0 on success. You should call drbd_md_sync() after you called
+ * this function.
+ */
+static int drbd_check_al_size(struct drbd_conf *mdev)
+{
+        struct lru_cache *n, *t;
+        struct lc_element *e;
+        unsigned int in_use;
+        int i;
+
+        ERR_IF(mdev->sync_conf.al_extents < 7)
+                mdev->sync_conf.al_extents = 127;
+
+        if (mdev->act_log &&
+            mdev->act_log->nr_elements == mdev->sync_conf.al_extents)
+                return 0;
+
+        in_use = 0;
+        t = mdev->act_log;
+        n = lc_create("act_log", drbd_al_ext_cache,
+                mdev->sync_conf.al_extents, sizeof(struct lc_element), 0);
+
+        if (n == NULL) {
+                dev_err(DEV, "Cannot allocate act_log lru!\n");
+                return -ENOMEM;
+        }
+        spin_lock_irq(&mdev->al_lock);
+        if (t) {
+                for (i = 0; i < t->nr_elements; i++) {
+                        e = lc_element_by_index(t, i);
+                        if (e->refcnt)
+                                dev_err(DEV, "refcnt(%d)==%d\n",
+                                    e->lc_number, e->refcnt);
+                        in_use += e->refcnt;
+                }
+        }
+        if (!in_use)
+                mdev->act_log = n;
+        spin_unlock_irq(&mdev->al_lock);
+        if (in_use) {
+                dev_err(DEV, "Activity log still in use!\n");
+                lc_destroy(n);
+                return -EBUSY;
+        } else {
+                if (t)
+                        lc_destroy(t);
+        }
+        drbd_md_mark_dirty(mdev); /* we changed mdev->act_log->nr_elemens */
+        return 0;
+}
+
+void drbd_setup_queue_param(struct drbd_conf *mdev, unsigned int max_seg_s) __must_hold(local)
+{
+        struct request_queue * const q = mdev->rq_queue;
+        struct request_queue * const b = mdev->ldev->backing_bdev->bd_disk->queue;
+        int max_segments = mdev->ldev->dc.max_bio_bvecs;
+
+        if (b->merge_bvec_fn && !mdev->ldev->dc.use_bmbv)
+                max_seg_s = PAGE_SIZE;
+
+        max_seg_s = min(queue_max_sectors(b) * queue_logical_block_size(b), max_seg_s);
+
+        blk_queue_max_sectors(q, max_seg_s >> 9);
+        blk_queue_max_phys_segments(q, max_segments ? max_segments : MAX_PHYS_SEGMENTS);
+        blk_queue_max_hw_segments(q, max_segments ? max_segments : MAX_HW_SEGMENTS);
+        blk_queue_max_segment_size(q, max_seg_s);
+        blk_queue_logical_block_size(q, 512);
+        blk_queue_segment_boundary(q, PAGE_SIZE-1);
+        blk_stack_limits(&q->limits, &b->limits, 0);
+
+        if (b->merge_bvec_fn)
+                dev_warn(DEV, "Backing device's merge_bvec_fn() = %p\n",
+                     b->merge_bvec_fn);
+        dev_info(DEV, "max_segment_size ( = BIO size ) = %u\n", queue_max_segment_size(q));
+
+        if (q->backing_dev_info.ra_pages != b->backing_dev_info.ra_pages) {
+                dev_info(DEV, "Adjusting my ra_pages to backing device's (%lu -> %lu)\n",
+                     q->backing_dev_info.ra_pages,
+                     b->backing_dev_info.ra_pages);
+                q->backing_dev_info.ra_pages = b->backing_dev_info.ra_pages;
+        }
+}
+
+/* serialize deconfig (worker exiting, doing cleanup)
+ * and reconfig (drbdsetup disk, drbdsetup net)
+ *
+ * wait for a potentially exiting worker, then restart it,
+ * or start a new one.
+ */
+static void drbd_reconfig_start(struct drbd_conf *mdev)
+{
+        wait_event(mdev->state_wait, test_and_set_bit(CONFIG_PENDING, &mdev->flags));
+        wait_event(mdev->state_wait, !test_bit(DEVICE_DYING, &mdev->flags));
+        drbd_thread_start(&mdev->worker);
+}
+
+/* if still unconfigured, stops worker again.
+ * if configured now, clears CONFIG_PENDING.
+ * wakes potential waiters */
+static void drbd_reconfig_done(struct drbd_conf *mdev)
+{
+        spin_lock_irq(&mdev->req_lock);
+        if (mdev->state.disk == D_DISKLESS &&
+            mdev->state.conn == C_STANDALONE &&
+            mdev->state.role == R_SECONDARY) {
+                set_bit(DEVICE_DYING, &mdev->flags);
+                drbd_thread_stop_nowait(&mdev->worker);
+        } else
+                clear_bit(CONFIG_PENDING, &mdev->flags);
+        spin_unlock_irq(&mdev->req_lock);
+        wake_up(&mdev->state_wait);
+}
+
+/* does always return 0;
+ * interesting return code is in reply->ret_code */
+static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                             struct drbd_nl_cfg_reply *reply)
+{
+        enum drbd_ret_codes retcode;
+        enum determine_dev_size dd;
+        sector_t max_possible_sectors;
+        sector_t min_md_device_sectors;
+        struct drbd_backing_dev *nbc = NULL; /* new_backing_conf */
+        struct inode *inode, *inode2;
+        struct lru_cache *resync_lru = NULL;
+        union drbd_state ns, os;
+        int rv;
+        int cp_discovered = 0;
+        int logical_block_size;
+
+        drbd_reconfig_start(mdev);
+
+        /* if you want to reconfigure, please tear down first */
+        if (mdev->state.disk > D_DISKLESS) {
+                retcode = ERR_DISK_CONFIGURED;
+                goto fail;
+        }
+
+        /* allocation not in the IO path, cqueue thread context */
+        nbc = kzalloc(sizeof(struct drbd_backing_dev), GFP_KERNEL);
+        if (!nbc) {
+                retcode = ERR_NOMEM;
+                goto fail;
+        }
+
+        nbc->dc.disk_size     = DRBD_DISK_SIZE_SECT_DEF;
+        nbc->dc.on_io_error   = DRBD_ON_IO_ERROR_DEF;
+        nbc->dc.fencing       = DRBD_FENCING_DEF;
+        nbc->dc.max_bio_bvecs = DRBD_MAX_BIO_BVECS_DEF;
+
+        if (!disk_conf_from_tags(mdev, nlp->tag_list, &nbc->dc)) {
+                retcode = ERR_MANDATORY_TAG;
+                goto fail;
+        }
+
+        if (nbc->dc.meta_dev_idx < DRBD_MD_INDEX_FLEX_INT) {
+                retcode = ERR_MD_IDX_INVALID;
+                goto fail;
+        }
+
+        nbc->lo_file = filp_open(nbc->dc.backing_dev, O_RDWR, 0);
+        if (IS_ERR(nbc->lo_file)) {
+                dev_err(DEV, "open(\"%s\") failed with %ld\n", nbc->dc.backing_dev,
+                    PTR_ERR(nbc->lo_file));
+                nbc->lo_file = NULL;
+                retcode = ERR_OPEN_DISK;
+                goto fail;
+        }
+
+        inode = nbc->lo_file->f_dentry->d_inode;
+
+        if (!S_ISBLK(inode->i_mode)) {
+                retcode = ERR_DISK_NOT_BDEV;
+                goto fail;
+        }
+
+        nbc->md_file = filp_open(nbc->dc.meta_dev, O_RDWR, 0);
+        if (IS_ERR(nbc->md_file)) {
+                dev_err(DEV, "open(\"%s\") failed with %ld\n", nbc->dc.meta_dev,
+                    PTR_ERR(nbc->md_file));
+                nbc->md_file = NULL;
+                retcode = ERR_OPEN_MD_DISK;
+                goto fail;
+        }
+
+        inode2 = nbc->md_file->f_dentry->d_inode;
+
+        if (!S_ISBLK(inode2->i_mode)) {
+                retcode = ERR_MD_NOT_BDEV;
+                goto fail;
+        }
+
+        nbc->backing_bdev = inode->i_bdev;
+        if (bd_claim(nbc->backing_bdev, mdev)) {
+                printk(KERN_ERR "drbd: bd_claim(%p,%p); failed [%p;%p;%u]\n",
+                       nbc->backing_bdev, mdev,
+                       nbc->backing_bdev->bd_holder,
+                       nbc->backing_bdev->bd_contains->bd_holder,
+                       nbc->backing_bdev->bd_holders);
+                retcode = ERR_BDCLAIM_DISK;
+                goto fail;
+        }
+
+        resync_lru = lc_create("resync", drbd_bm_ext_cache,
+                        61, sizeof(struct bm_extent),
+                        offsetof(struct bm_extent, lce));
+        if (!resync_lru) {
+                retcode = ERR_NOMEM;
+                goto release_bdev_fail;
+        }
+
+        /* meta_dev_idx >= 0: external fixed size,
+         * possibly multiple drbd sharing one meta device.
+         * TODO in that case, paranoia check that [md_bdev, meta_dev_idx] is
+         * not yet used by some other drbd minor!
+         * (if you use drbd.conf + drbdadm,
+         * that should check it for you already; but if you don't, or someone
+         * fooled it, we need to double check here) */
+        nbc->md_bdev = inode2->i_bdev;
+        if (bd_claim(nbc->md_bdev, (nbc->dc.meta_dev_idx < 0) ? (void *)mdev
+                                : (void *) drbd_m_holder)) {
+                retcode = ERR_BDCLAIM_MD_DISK;
+                goto release_bdev_fail;
+        }
+
+        if ((nbc->backing_bdev == nbc->md_bdev) !=
+            (nbc->dc.meta_dev_idx == DRBD_MD_INDEX_INTERNAL ||
+             nbc->dc.meta_dev_idx == DRBD_MD_INDEX_FLEX_INT)) {
+                retcode = ERR_MD_IDX_INVALID;
+                goto release_bdev2_fail;
+        }
+
+        /* RT - for drbd_get_max_capacity() DRBD_MD_INDEX_FLEX_INT */
+        drbd_md_set_sector_offsets(mdev, nbc);
+
+        if (drbd_get_max_capacity(nbc) < nbc->dc.disk_size) {
+                dev_err(DEV, "max capacity %llu smaller than disk size %llu\n",
+                        (unsigned long long) drbd_get_max_capacity(nbc),
+                        (unsigned long long) nbc->dc.disk_size);
+                retcode = ERR_DISK_TO_SMALL;
+                goto release_bdev2_fail;
+        }
+
+        if (nbc->dc.meta_dev_idx < 0) {
+                max_possible_sectors = DRBD_MAX_SECTORS_FLEX;
+                /* at least one MB, otherwise it does not make sense */
+                min_md_device_sectors = (2<<10);
+        } else {
+                max_possible_sectors = DRBD_MAX_SECTORS;
+                min_md_device_sectors = MD_RESERVED_SECT * (nbc->dc.meta_dev_idx + 1);
+        }
+
+        if (drbd_get_capacity(nbc->md_bdev) > max_possible_sectors)
+                dev_warn(DEV, "truncating very big lower level device "
+                     "to currently maximum possible %llu sectors\n",
+                     (unsigned long long) max_possible_sectors);
+
+        if (drbd_get_capacity(nbc->md_bdev) < min_md_device_sectors) {
+                retcode = ERR_MD_DISK_TO_SMALL;
+                dev_warn(DEV, "refusing attach: md-device too small, "
+                     "at least %llu sectors needed for this meta-disk type\n",
+                     (unsigned long long) min_md_device_sectors);
+                goto release_bdev2_fail;
+        }
+
+        /* Make sure the new disk is big enough
+         * (we may currently be R_PRIMARY with no local disk...) */
+        if (drbd_get_max_capacity(nbc) <
+            drbd_get_capacity(mdev->this_bdev)) {
+                retcode = ERR_DISK_TO_SMALL;
+                goto release_bdev2_fail;
+        }
+
+        nbc->known_size = drbd_get_capacity(nbc->backing_bdev);
+
+        drbd_suspend_io(mdev);
+        /* also wait for the last barrier ack. */
+        wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_pending_cnt));
+        /* and for any other previously queued work */
+        drbd_flush_workqueue(mdev);
+
+        retcode = _drbd_request_state(mdev, NS(disk, D_ATTACHING), CS_VERBOSE);
+        drbd_resume_io(mdev);
+        if (retcode < SS_SUCCESS)
+                goto release_bdev2_fail;
+
+        if (!get_ldev_if_state(mdev, D_ATTACHING))
+                goto force_diskless;
+
+        drbd_md_set_sector_offsets(mdev, nbc);
+
+        if (!mdev->bitmap) {
+                if (drbd_bm_init(mdev)) {
+                        retcode = ERR_NOMEM;
+                        goto force_diskless_dec;
+                }
+        }
+
+        retcode = drbd_md_read(mdev, nbc);
+        if (retcode != NO_ERROR)
+                goto force_diskless_dec;
+
+        if (mdev->state.conn < C_CONNECTED &&
+            mdev->state.role == R_PRIMARY &&
+            (mdev->ed_uuid & ~((u64)1)) != (nbc->md.uuid[UI_CURRENT] & ~((u64)1))) {
+                dev_err(DEV, "Can only attach to data with current UUID=%016llX\n",
+                    (unsigned long long)mdev->ed_uuid);
+                retcode = ERR_DATA_NOT_CURRENT;
+                goto force_diskless_dec;
+        }
+
+        /* Since we are diskless, fix the activity log first... */
+        if (drbd_check_al_size(mdev)) {
+                retcode = ERR_NOMEM;
+                goto force_diskless_dec;
+        }
+
+        /* Prevent shrinking of consistent devices ! */
+        if (drbd_md_test_flag(nbc, MDF_CONSISTENT) &&
+           drbd_new_dev_size(mdev, nbc) < nbc->md.la_size_sect) {
+                dev_warn(DEV, "refusing to truncate a consistent device\n");
+                retcode = ERR_DISK_TO_SMALL;
+                goto force_diskless_dec;
+        }
+
+        if (!drbd_al_read_log(mdev, nbc)) {
+                retcode = ERR_IO_MD_DISK;
+                goto force_diskless_dec;
+        }
+
+        /* allocate a second IO page if logical_block_size != 512 */
+        logical_block_size = bdev_logical_block_size(nbc->md_bdev);
+        if (logical_block_size == 0)
+                logical_block_size = MD_SECTOR_SIZE;
+
+        if (logical_block_size != MD_SECTOR_SIZE) {
+                if (!mdev->md_io_tmpp) {
+                        struct page *page = alloc_page(GFP_NOIO);
+                        if (!page)
+                                goto force_diskless_dec;
+
+                        dev_warn(DEV, "Meta data's bdev logical_block_size = %d != %d\n",
+                             logical_block_size, MD_SECTOR_SIZE);
+                        dev_warn(DEV, "Workaround engaged (has performance impact).\n");
+
+                        mdev->md_io_tmpp = page;
+                }
+        }
+
+        /* Reset the "barriers don't work" bits here, then force meta data to
+         * be written, to ensure we determine if barriers are supported. */
+        if (nbc->dc.no_md_flush)
+                set_bit(MD_NO_BARRIER, &mdev->flags);
+        else
+                clear_bit(MD_NO_BARRIER, &mdev->flags);
+
+        /* Point of no return reached.
+         * Devices and memory are no longer released by error cleanup below.
+         * now mdev takes over responsibility, and the state engine should
+         * clean it up somewhere.  */
+        D_ASSERT(mdev->ldev == NULL);
+        mdev->ldev = nbc;
+        mdev->resync = resync_lru;
+        nbc = NULL;
+        resync_lru = NULL;
+
+        mdev->write_ordering = WO_bio_barrier;
+        drbd_bump_write_ordering(mdev, WO_bio_barrier);
+
+        if (drbd_md_test_flag(mdev->ldev, MDF_CRASHED_PRIMARY))
+                set_bit(CRASHED_PRIMARY, &mdev->flags);
+        else
+                clear_bit(CRASHED_PRIMARY, &mdev->flags);
+
+        if (drbd_md_test_flag(mdev->ldev, MDF_PRIMARY_IND)) {
+                set_bit(CRASHED_PRIMARY, &mdev->flags);
+                cp_discovered = 1;
+        }
+
+        mdev->send_cnt = 0;
+        mdev->recv_cnt = 0;
+        mdev->read_cnt = 0;
+        mdev->writ_cnt = 0;
+
+        drbd_setup_queue_param(mdev, DRBD_MAX_SEGMENT_SIZE);
+
+        /* If I am currently not R_PRIMARY,
+         * but meta data primary indicator is set,
+         * I just now recover from a hard crash,
+         * and have been R_PRIMARY before that crash.
+         *
+         * Now, if I had no connection before that crash
+         * (have been degraded R_PRIMARY), chances are that
+         * I won't find my peer now either.
+         *
+         * In that case, and _only_ in that case,
+         * we use the degr-wfc-timeout instead of the default,
+         * so we can automatically recover from a crash of a
+         * degraded but active "cluster" after a certain timeout.
+         */
+        clear_bit(USE_DEGR_WFC_T, &mdev->flags);
+        if (mdev->state.role != R_PRIMARY &&
+             drbd_md_test_flag(mdev->ldev, MDF_PRIMARY_IND) &&
+            !drbd_md_test_flag(mdev->ldev, MDF_CONNECTED_IND))
+                set_bit(USE_DEGR_WFC_T, &mdev->flags);
+
+        dd = drbd_determin_dev_size(mdev);
+        if (dd == dev_size_error) {
+                retcode = ERR_NOMEM_BITMAP;
+                goto force_diskless_dec;
+        } else if (dd == grew)
+                set_bit(RESYNC_AFTER_NEG, &mdev->flags);
+
+        if (drbd_md_test_flag(mdev->ldev, MDF_FULL_SYNC)) {
+                dev_info(DEV, "Assuming that all blocks are out of sync "
+                     "(aka FullSync)\n");
+                if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from attaching")) {
+                        retcode = ERR_IO_MD_DISK;
+                        goto force_diskless_dec;
+                }
+        } else {
+                if (drbd_bitmap_io(mdev, &drbd_bm_read, "read from attaching") < 0) {
+                        retcode = ERR_IO_MD_DISK;
+                        goto force_diskless_dec;
+                }
+        }
+
+        if (cp_discovered) {
+                drbd_al_apply_to_bm(mdev);
+                drbd_al_to_on_disk_bm(mdev);
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        os = mdev->state;
+        ns.i = os.i;
+        /* If MDF_CONSISTENT is not set go into inconsistent state,
+           otherwise investigate MDF_WasUpToDate...
+           If MDF_WAS_UP_TO_DATE is not set go into D_OUTDATED disk state,
+           otherwise into D_CONSISTENT state.
+        */
+        if (drbd_md_test_flag(mdev->ldev, MDF_CONSISTENT)) {
+                if (drbd_md_test_flag(mdev->ldev, MDF_WAS_UP_TO_DATE))
+                        ns.disk = D_CONSISTENT;
+                else
+                        ns.disk = D_OUTDATED;
+        } else {
+                ns.disk = D_INCONSISTENT;
+        }
+
+        if (drbd_md_test_flag(mdev->ldev, MDF_PEER_OUT_DATED))
+                ns.pdsk = D_OUTDATED;
+
+        if ( ns.disk == D_CONSISTENT &&
+            (ns.pdsk == D_OUTDATED || mdev->ldev->dc.fencing == FP_DONT_CARE))
+                ns.disk = D_UP_TO_DATE;
+
+        /* All tests on MDF_PRIMARY_IND, MDF_CONNECTED_IND,
+           MDF_CONSISTENT and MDF_WAS_UP_TO_DATE must happen before
+           this point, because drbd_request_state() modifies these
+           flags. */
+
+        /* In case we are C_CONNECTED postpone any decision on the new disk
+           state after the negotiation phase. */
+        if (mdev->state.conn == C_CONNECTED) {
+                mdev->new_state_tmp.i = ns.i;
+                ns.i = os.i;
+                ns.disk = D_NEGOTIATING;
+        }
+
+        rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+        ns = mdev->state;
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (rv < SS_SUCCESS)
+                goto force_diskless_dec;
+
+        if (mdev->state.role == R_PRIMARY)
+                mdev->ldev->md.uuid[UI_CURRENT] |=  (u64)1;
+        else
+                mdev->ldev->md.uuid[UI_CURRENT] &= ~(u64)1;
+
+        drbd_md_mark_dirty(mdev);
+        drbd_md_sync(mdev);
+
+        kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+        put_ldev(mdev);
+        reply->ret_code = retcode;
+        drbd_reconfig_done(mdev);
+        return 0;
+
+ force_diskless_dec:
+        put_ldev(mdev);
+ force_diskless:
+        drbd_force_state(mdev, NS(disk, D_DISKLESS));
+        drbd_md_sync(mdev);
+ release_bdev2_fail:
+        if (nbc)
+                bd_release(nbc->md_bdev);
+ release_bdev_fail:
+        if (nbc)
+                bd_release(nbc->backing_bdev);
+ fail:
+        if (nbc) {
+                if (nbc->lo_file)
+                        fput(nbc->lo_file);
+                if (nbc->md_file)
+                        fput(nbc->md_file);
+                kfree(nbc);
+        }
+        lc_destroy(resync_lru);
+
+        reply->ret_code = retcode;
+        drbd_reconfig_done(mdev);
+        return 0;
+}
+
+static int drbd_nl_detach(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                          struct drbd_nl_cfg_reply *reply)
+{
+        reply->ret_code = drbd_request_state(mdev, NS(disk, D_DISKLESS));
+        return 0;
+}
+
+static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                            struct drbd_nl_cfg_reply *reply)
+{
+        int i, ns;
+        enum drbd_ret_codes retcode;
+        struct net_conf *new_conf = NULL;
+        struct crypto_hash *tfm = NULL;
+        struct crypto_hash *integrity_w_tfm = NULL;
+        struct crypto_hash *integrity_r_tfm = NULL;
+        struct hlist_head *new_tl_hash = NULL;
+        struct hlist_head *new_ee_hash = NULL;
+        struct drbd_conf *odev;
+        char hmac_name[CRYPTO_MAX_ALG_NAME];
+        void *int_dig_out = NULL;
+        void *int_dig_in = NULL;
+        void *int_dig_vv = NULL;
+        struct sockaddr *new_my_addr, *new_peer_addr, *taken_addr;
+
+        drbd_reconfig_start(mdev);
+
+        if (mdev->state.conn > C_STANDALONE) {
+                retcode = ERR_NET_CONFIGURED;
+                goto fail;
+        }
+
+        /* allocation not in the IO path, cqueue thread context */
+        new_conf = kmalloc(sizeof(struct net_conf), GFP_KERNEL);
+        if (!new_conf) {
+                retcode = ERR_NOMEM;
+                goto fail;
+        }
+
+        memset(new_conf, 0, sizeof(struct net_conf));
+        new_conf->timeout          = DRBD_TIMEOUT_DEF;
+        new_conf->try_connect_int  = DRBD_CONNECT_INT_DEF;
+        new_conf->ping_int         = DRBD_PING_INT_DEF;
+        new_conf->max_epoch_size   = DRBD_MAX_EPOCH_SIZE_DEF;
+        new_conf->max_buffers      = DRBD_MAX_BUFFERS_DEF;
+        new_conf->unplug_watermark = DRBD_UNPLUG_WATERMARK_DEF;
+        new_conf->sndbuf_size      = DRBD_SNDBUF_SIZE_DEF;
+        new_conf->rcvbuf_size      = DRBD_RCVBUF_SIZE_DEF;
+        new_conf->ko_count         = DRBD_KO_COUNT_DEF;
+        new_conf->after_sb_0p      = DRBD_AFTER_SB_0P_DEF;
+        new_conf->after_sb_1p      = DRBD_AFTER_SB_1P_DEF;
+        new_conf->after_sb_2p      = DRBD_AFTER_SB_2P_DEF;
+        new_conf->want_lose        = 0;
+        new_conf->two_primaries    = 0;
+        new_conf->wire_protocol    = DRBD_PROT_C;
+        new_conf->ping_timeo       = DRBD_PING_TIMEO_DEF;
+        new_conf->rr_conflict      = DRBD_RR_CONFLICT_DEF;
+
+        if (!net_conf_from_tags(mdev, nlp->tag_list, new_conf)) {
+                retcode = ERR_MANDATORY_TAG;
+                goto fail;
+        }
+
+        if (new_conf->two_primaries
+            && (new_conf->wire_protocol != DRBD_PROT_C)) {
+                retcode = ERR_NOT_PROTO_C;
+                goto fail;
+        };
+
+        if (mdev->state.role == R_PRIMARY && new_conf->want_lose) {
+                retcode = ERR_DISCARD;
+                goto fail;
+        }
+
+        retcode = NO_ERROR;
+
+        new_my_addr = (struct sockaddr *)&new_conf->my_addr;
+        new_peer_addr = (struct sockaddr *)&new_conf->peer_addr;
+        for (i = 0; i < minor_count; i++) {
+                odev = minor_to_mdev(i);
+                if (!odev || odev == mdev)
+                        continue;
+                if (get_net_conf(odev)) {
+                        taken_addr = (struct sockaddr *)&odev->net_conf->my_addr;
+                        if (new_conf->my_addr_len == odev->net_conf->my_addr_len &&
+                            !memcmp(new_my_addr, taken_addr, new_conf->my_addr_len))
+                                retcode = ERR_LOCAL_ADDR;
+
+                        taken_addr = (struct sockaddr *)&odev->net_conf->peer_addr;
+                        if (new_conf->peer_addr_len == odev->net_conf->peer_addr_len &&
+                            !memcmp(new_peer_addr, taken_addr, new_conf->peer_addr_len))
+                                retcode = ERR_PEER_ADDR;
+
+                        put_net_conf(odev);
+                        if (retcode != NO_ERROR)
+                                goto fail;
+                }
+        }
+
+        if (new_conf->cram_hmac_alg[0] != 0) {
+                snprintf(hmac_name, CRYPTO_MAX_ALG_NAME, "hmac(%s)",
+                        new_conf->cram_hmac_alg);
+                tfm = crypto_alloc_hash(hmac_name, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(tfm)) {
+                        tfm = NULL;
+                        retcode = ERR_AUTH_ALG;
+                        goto fail;
+                }
+
+                if (crypto_tfm_alg_type(crypto_hash_tfm(tfm))
+                                                != CRYPTO_ALG_TYPE_HASH) {
+                        retcode = ERR_AUTH_ALG_ND;
+                        goto fail;
+                }
+        }
+
+        if (new_conf->integrity_alg[0]) {
+                integrity_w_tfm = crypto_alloc_hash(new_conf->integrity_alg, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(integrity_w_tfm)) {
+                        integrity_w_tfm = NULL;
+                        retcode=ERR_INTEGRITY_ALG;
+                        goto fail;
+                }
+
+                if (!drbd_crypto_is_hash(crypto_hash_tfm(integrity_w_tfm))) {
+                        retcode=ERR_INTEGRITY_ALG_ND;
+                        goto fail;
+                }
+
+                integrity_r_tfm = crypto_alloc_hash(new_conf->integrity_alg, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(integrity_r_tfm)) {
+                        integrity_r_tfm = NULL;
+                        retcode=ERR_INTEGRITY_ALG;
+                        goto fail;
+                }
+        }
+
+        ns = new_conf->max_epoch_size/8;
+        if (mdev->tl_hash_s != ns) {
+                new_tl_hash = kzalloc(ns*sizeof(void *), GFP_KERNEL);
+                if (!new_tl_hash) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+        }
+
+        ns = new_conf->max_buffers/8;
+        if (new_conf->two_primaries && (mdev->ee_hash_s != ns)) {
+                new_ee_hash = kzalloc(ns*sizeof(void *), GFP_KERNEL);
+                if (!new_ee_hash) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+        }
+
+        ((char *)new_conf->shared_secret)[SHARED_SECRET_MAX-1] = 0;
+
+        if (integrity_w_tfm) {
+                i = crypto_hash_digestsize(integrity_w_tfm);
+                int_dig_out = kmalloc(i, GFP_KERNEL);
+                if (!int_dig_out) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+                int_dig_in = kmalloc(i, GFP_KERNEL);
+                if (!int_dig_in) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+                int_dig_vv = kmalloc(i, GFP_KERNEL);
+                if (!int_dig_vv) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+        }
+
+        if (!mdev->bitmap) {
+                if(drbd_bm_init(mdev)) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        if (mdev->net_conf != NULL) {
+                retcode = ERR_NET_CONFIGURED;
+                spin_unlock_irq(&mdev->req_lock);
+                goto fail;
+        }
+        mdev->net_conf = new_conf;
+
+        mdev->send_cnt = 0;
+        mdev->recv_cnt = 0;
+
+        if (new_tl_hash) {
+                kfree(mdev->tl_hash);
+                mdev->tl_hash_s = mdev->net_conf->max_epoch_size/8;
+                mdev->tl_hash = new_tl_hash;
+        }
+
+        if (new_ee_hash) {
+                kfree(mdev->ee_hash);
+                mdev->ee_hash_s = mdev->net_conf->max_buffers/8;
+                mdev->ee_hash = new_ee_hash;
+        }
+
+        crypto_free_hash(mdev->cram_hmac_tfm);
+        mdev->cram_hmac_tfm = tfm;
+
+        crypto_free_hash(mdev->integrity_w_tfm);
+        mdev->integrity_w_tfm = integrity_w_tfm;
+
+        crypto_free_hash(mdev->integrity_r_tfm);
+        mdev->integrity_r_tfm = integrity_r_tfm;
+
+        kfree(mdev->int_dig_out);
+        kfree(mdev->int_dig_in);
+        kfree(mdev->int_dig_vv);
+        mdev->int_dig_out=int_dig_out;
+        mdev->int_dig_in=int_dig_in;
+        mdev->int_dig_vv=int_dig_vv;
+        spin_unlock_irq(&mdev->req_lock);
+
+        retcode = _drbd_request_state(mdev, NS(conn, C_UNCONNECTED), CS_VERBOSE);
+
+        kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+        reply->ret_code = retcode;
+        drbd_reconfig_done(mdev);
+        return 0;
+
+fail:
+        kfree(int_dig_out);
+        kfree(int_dig_in);
+        kfree(int_dig_vv);
+        crypto_free_hash(tfm);
+        crypto_free_hash(integrity_w_tfm);
+        crypto_free_hash(integrity_r_tfm);
+        kfree(new_tl_hash);
+        kfree(new_ee_hash);
+        kfree(new_conf);
+
+        reply->ret_code = retcode;
+        drbd_reconfig_done(mdev);
+        return 0;
+}
+
+static int drbd_nl_disconnect(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                              struct drbd_nl_cfg_reply *reply)
+{
+        int retcode;
+
+        retcode = _drbd_request_state(mdev, NS(conn, C_DISCONNECTING), CS_ORDERED);
+
+        if (retcode == SS_NOTHING_TO_DO)
+                goto done;
+        else if (retcode == SS_ALREADY_STANDALONE)
+                goto done;
+        else if (retcode == SS_PRIMARY_NOP) {
+                /* Our statche checking code wants to see the peer outdated. */
+                retcode = drbd_request_state(mdev, NS2(conn, C_DISCONNECTING,
+                                                      pdsk, D_OUTDATED));
+        } else if (retcode == SS_CW_FAILED_BY_PEER) {
+                /* The peer probably wants to see us outdated. */
+                retcode = _drbd_request_state(mdev, NS2(conn, C_DISCONNECTING,
+                                                        disk, D_OUTDATED),
+                                              CS_ORDERED);
+                if (retcode == SS_IS_DISKLESS || retcode == SS_LOWER_THAN_OUTDATED) {
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                        retcode = SS_SUCCESS;
+                }
+        }
+
+        if (retcode < SS_SUCCESS)
+                goto fail;
+
+        if (wait_event_interruptible(mdev->state_wait,
+                                     mdev->state.conn != C_DISCONNECTING)) {
+                /* Do not test for mdev->state.conn == C_STANDALONE, since
+                   someone else might connect us in the mean time! */
+                retcode = ERR_INTR;
+                goto fail;
+        }
+
+ done:
+        retcode = NO_ERROR;
+ fail:
+        drbd_md_sync(mdev);
+        reply->ret_code = retcode;
+        return 0;
+}
+
+void resync_after_online_grow(struct drbd_conf *mdev)
+{
+        int iass; /* I am sync source */
+
+        dev_info(DEV, "Resync of new storage after online grow\n");
+        if (mdev->state.role != mdev->state.peer)
+                iass = (mdev->state.role == R_PRIMARY);
+        else
+                iass = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+
+        if (iass)
+                drbd_start_resync(mdev, C_SYNC_SOURCE);
+        else
+                _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE + CS_SERIALIZE);
+}
+
+static int drbd_nl_resize(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                          struct drbd_nl_cfg_reply *reply)
+{
+        struct resize rs;
+        int retcode = NO_ERROR;
+        int ldsc = 0; /* local disk size changed */
+        enum determine_dev_size dd;
+
+        memset(&rs, 0, sizeof(struct resize));
+        if (!resize_from_tags(mdev, nlp->tag_list, &rs)) {
+                retcode = ERR_MANDATORY_TAG;
+                goto fail;
+        }
+
+        if (mdev->state.conn > C_CONNECTED) {
+                retcode = ERR_RESIZE_RESYNC;
+                goto fail;
+        }
+
+        if (mdev->state.role == R_SECONDARY &&
+            mdev->state.peer == R_SECONDARY) {
+                retcode = ERR_NO_PRIMARY;
+                goto fail;
+        }
+
+        if (!get_ldev(mdev)) {
+                retcode = ERR_NO_DISK;
+                goto fail;
+        }
+
+        if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
+                mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+                ldsc = 1;
+        }
+
+        mdev->ldev->dc.disk_size = (sector_t)rs.resize_size;
+        dd = drbd_determin_dev_size(mdev);
+        drbd_md_sync(mdev);
+        put_ldev(mdev);
+        if (dd == dev_size_error) {
+                retcode = ERR_NOMEM_BITMAP;
+                goto fail;
+        }
+
+        if (mdev->state.conn == C_CONNECTED && (dd != unchanged || ldsc)) {
+                if (dd == grew)
+                        set_bit(RESIZE_PENDING, &mdev->flags);
+
+                drbd_send_uuids(mdev);
+                drbd_send_sizes(mdev, 1);
+        }
+
+ fail:
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                               struct drbd_nl_cfg_reply *reply)
+{
+        int retcode = NO_ERROR;
+        int err;
+        int ovr; /* online verify running */
+        int rsr; /* re-sync running */
+        struct crypto_hash *verify_tfm = NULL;
+        struct crypto_hash *csums_tfm = NULL;
+        struct syncer_conf sc;
+        cpumask_var_t new_cpu_mask;
+
+        if (!zalloc_cpumask_var(&new_cpu_mask, GFP_KERNEL)) {
+                retcode = ERR_NOMEM;
+                goto fail;
+        }
+
+        if (nlp->flags & DRBD_NL_SET_DEFAULTS) {
+                memset(&sc, 0, sizeof(struct syncer_conf));
+                sc.rate       = DRBD_RATE_DEF;
+                sc.after      = DRBD_AFTER_DEF;
+                sc.al_extents = DRBD_AL_EXTENTS_DEF;
+        } else
+                memcpy(&sc, &mdev->sync_conf, sizeof(struct syncer_conf));
+
+        if (!syncer_conf_from_tags(mdev, nlp->tag_list, &sc)) {
+                retcode = ERR_MANDATORY_TAG;
+                goto fail;
+        }
+
+        /* re-sync running */
+        rsr = ( mdev->state.conn == C_SYNC_SOURCE ||
+                mdev->state.conn == C_SYNC_TARGET ||
+                mdev->state.conn == C_PAUSED_SYNC_S ||
+                mdev->state.conn == C_PAUSED_SYNC_T );
+
+        if (rsr && strcmp(sc.csums_alg, mdev->sync_conf.csums_alg)) {
+                retcode = ERR_CSUMS_RESYNC_RUNNING;
+                goto fail;
+        }
+
+        if (!rsr && sc.csums_alg[0]) {
+                csums_tfm = crypto_alloc_hash(sc.csums_alg, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(csums_tfm)) {
+                        csums_tfm = NULL;
+                        retcode = ERR_CSUMS_ALG;
+                        goto fail;
+                }
+
+                if (!drbd_crypto_is_hash(crypto_hash_tfm(csums_tfm))) {
+                        retcode = ERR_CSUMS_ALG_ND;
+                        goto fail;
+                }
+        }
+
+        /* online verify running */
+        ovr = (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T);
+
+        if (ovr) {
+                if (strcmp(sc.verify_alg, mdev->sync_conf.verify_alg)) {
+                        retcode = ERR_VERIFY_RUNNING;
+                        goto fail;
+                }
+        }
+
+        if (!ovr && sc.verify_alg[0]) {
+                verify_tfm = crypto_alloc_hash(sc.verify_alg, 0, CRYPTO_ALG_ASYNC);
+                if (IS_ERR(verify_tfm)) {
+                        verify_tfm = NULL;
+                        retcode = ERR_VERIFY_ALG;
+                        goto fail;
+                }
+
+                if (!drbd_crypto_is_hash(crypto_hash_tfm(verify_tfm))) {
+                        retcode = ERR_VERIFY_ALG_ND;
+                        goto fail;
+                }
+        }
+
+        /* silently ignore cpu mask on UP kernel */
+        if (nr_cpu_ids > 1 && sc.cpu_mask[0] != 0) {
+                err = __bitmap_parse(sc.cpu_mask, 32, 0,
+                                cpumask_bits(new_cpu_mask), nr_cpu_ids);
+                if (err) {
+                        dev_warn(DEV, "__bitmap_parse() failed with %d\n", err);
+                        retcode = ERR_CPU_MASK_PARSE;
+                        goto fail;
+                }
+        }
+
+        ERR_IF (sc.rate < 1) sc.rate = 1;
+        ERR_IF (sc.al_extents < 7) sc.al_extents = 127; /* arbitrary minimum */
+#define AL_MAX ((MD_AL_MAX_SIZE-1) * AL_EXTENTS_PT)
+        if (sc.al_extents > AL_MAX) {
+                dev_err(DEV, "sc.al_extents > %d\n", AL_MAX);
+                sc.al_extents = AL_MAX;
+        }
+#undef AL_MAX
+
+        /* most sanity checks done, try to assign the new sync-after
+         * dependency.  need to hold the global lock in there,
+         * to avoid a race in the dependency loop check. */
+        retcode = drbd_alter_sa(mdev, sc.after);
+        if (retcode != NO_ERROR)
+                goto fail;
+
+        /* ok, assign the rest of it as well.
+         * lock against receive_SyncParam() */
+        spin_lock(&mdev->peer_seq_lock);
+        mdev->sync_conf = sc;
+
+        if (!rsr) {
+                crypto_free_hash(mdev->csums_tfm);
+                mdev->csums_tfm = csums_tfm;
+                csums_tfm = NULL;
+        }
+
+        if (!ovr) {
+                crypto_free_hash(mdev->verify_tfm);
+                mdev->verify_tfm = verify_tfm;
+                verify_tfm = NULL;
+        }
+        spin_unlock(&mdev->peer_seq_lock);
+
+        if (get_ldev(mdev)) {
+                wait_event(mdev->al_wait, lc_try_lock(mdev->act_log));
+                drbd_al_shrink(mdev);
+                err = drbd_check_al_size(mdev);
+                lc_unlock(mdev->act_log);
+                wake_up(&mdev->al_wait);
+
+                put_ldev(mdev);
+                drbd_md_sync(mdev);
+
+                if (err) {
+                        retcode = ERR_NOMEM;
+                        goto fail;
+                }
+        }
+
+        if (mdev->state.conn >= C_CONNECTED)
+                drbd_send_sync_param(mdev, &sc);
+
+        if (!cpumask_equal(mdev->cpu_mask, new_cpu_mask)) {
+                cpumask_copy(mdev->cpu_mask, new_cpu_mask);
+                drbd_calc_cpu_mask(mdev);
+                mdev->receiver.reset_cpu_mask = 1;
+                mdev->asender.reset_cpu_mask = 1;
+                mdev->worker.reset_cpu_mask = 1;
+        }
+
+        kobject_uevent(&disk_to_dev(mdev->vdisk)->kobj, KOBJ_CHANGE);
+fail:
+        free_cpumask_var(new_cpu_mask);
+        crypto_free_hash(csums_tfm);
+        crypto_free_hash(verify_tfm);
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static int drbd_nl_invalidate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                              struct drbd_nl_cfg_reply *reply)
+{
+        int retcode;
+
+        retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T), CS_ORDERED);
+
+        if (retcode < SS_SUCCESS && retcode != SS_NEED_CONNECTION)
+                retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
+
+        while (retcode == SS_NEED_CONNECTION) {
+                spin_lock_irq(&mdev->req_lock);
+                if (mdev->state.conn < C_CONNECTED)
+                        retcode = _drbd_set_state(_NS(mdev, disk, D_INCONSISTENT), CS_VERBOSE, NULL);
+                spin_unlock_irq(&mdev->req_lock);
+
+                if (retcode != SS_NEED_CONNECTION)
+                        break;
+
+                retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
+        }
+
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                                   struct drbd_nl_cfg_reply *reply)
+{
+
+        reply->ret_code = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S));
+
+        return 0;
+}
+
+static int drbd_nl_pause_sync(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                              struct drbd_nl_cfg_reply *reply)
+{
+        int retcode = NO_ERROR;
+
+        if (drbd_request_state(mdev, NS(user_isp, 1)) == SS_NOTHING_TO_DO)
+                retcode = ERR_PAUSE_IS_SET;
+
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static int drbd_nl_resume_sync(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                               struct drbd_nl_cfg_reply *reply)
+{
+        int retcode = NO_ERROR;
+
+        if (drbd_request_state(mdev, NS(user_isp, 0)) == SS_NOTHING_TO_DO)
+                retcode = ERR_PAUSE_IS_CLEAR;
+
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static int drbd_nl_suspend_io(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                              struct drbd_nl_cfg_reply *reply)
+{
+        reply->ret_code = drbd_request_state(mdev, NS(susp, 1));
+
+        return 0;
+}
+
+static int drbd_nl_resume_io(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                             struct drbd_nl_cfg_reply *reply)
+{
+        reply->ret_code = drbd_request_state(mdev, NS(susp, 0));
+        return 0;
+}
+
+static int drbd_nl_outdate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                           struct drbd_nl_cfg_reply *reply)
+{
+        reply->ret_code = drbd_request_state(mdev, NS(disk, D_OUTDATED));
+        return 0;
+}
+
+static int drbd_nl_get_config(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                           struct drbd_nl_cfg_reply *reply)
+{
+        unsigned short *tl;
+
+        tl = reply->tag_list;
+
+        if (get_ldev(mdev)) {
+                tl = disk_conf_to_tags(mdev, &mdev->ldev->dc, tl);
+                put_ldev(mdev);
+        }
+
+        if (get_net_conf(mdev)) {
+                tl = net_conf_to_tags(mdev, mdev->net_conf, tl);
+                put_net_conf(mdev);
+        }
+        tl = syncer_conf_to_tags(mdev, &mdev->sync_conf, tl);
+
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_get_state(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                             struct drbd_nl_cfg_reply *reply)
+{
+        unsigned short *tl = reply->tag_list;
+        union drbd_state s = mdev->state;
+        unsigned long rs_left;
+        unsigned int res;
+
+        tl = get_state_to_tags(mdev, (struct get_state *)&s, tl);
+
+        /* no local ref, no bitmap, no syncer progress. */
+        if (s.conn >= C_SYNC_SOURCE && s.conn <= C_PAUSED_SYNC_T) {
+                if (get_ldev(mdev)) {
+                        drbd_get_syncer_progress(mdev, &rs_left, &res);
+                        tl = tl_add_int(tl, T_sync_progress, &res);
+                        put_ldev(mdev);
+                }
+        }
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_get_uuids(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                             struct drbd_nl_cfg_reply *reply)
+{
+        unsigned short *tl;
+
+        tl = reply->tag_list;
+
+        if (get_ldev(mdev)) {
+                tl = tl_add_blob(tl, T_uuids, mdev->ldev->md.uuid, UI_SIZE*sizeof(u64));
+                tl = tl_add_int(tl, T_uuids_flags, &mdev->ldev->md.flags);
+                put_ldev(mdev);
+        }
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+/**
+ * drbd_nl_get_timeout_flag() - Used by drbdsetup to find out which timeout value to use
+ * @mdev:       DRBD device.
+ * @nlp:        Netlink/connector packet from drbdsetup
+ * @reply:      Reply packet for drbdsetup
+ */
+static int drbd_nl_get_timeout_flag(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                                    struct drbd_nl_cfg_reply *reply)
+{
+        unsigned short *tl;
+        char rv;
+
+        tl = reply->tag_list;
+
+        rv = mdev->state.pdsk == D_OUTDATED        ? UT_PEER_OUTDATED :
+          test_bit(USE_DEGR_WFC_T, &mdev->flags) ? UT_DEGRADED : UT_DEFAULT;
+
+        tl = tl_add_blob(tl, T_use_degraded, &rv, sizeof(rv));
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        return (int)((char *)tl - (char *)reply->tag_list);
+}
+
+static int drbd_nl_start_ov(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                                    struct drbd_nl_cfg_reply *reply)
+{
+        /* default to resume from last known position, if possible */
+        struct start_ov args =
+                { .start_sector = mdev->ov_start_sector };
+
+        if (!start_ov_from_tags(mdev, nlp->tag_list, &args)) {
+                reply->ret_code = ERR_MANDATORY_TAG;
+                return 0;
+        }
+        /* w_make_ov_request expects position to be aligned */
+        mdev->ov_start_sector = args.start_sector & ~BM_SECT_PER_BIT;
+        reply->ret_code = drbd_request_state(mdev,NS(conn,C_VERIFY_S));
+        return 0;
+}
+
+
+static int drbd_nl_new_c_uuid(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
+                              struct drbd_nl_cfg_reply *reply)
+{
+        int retcode = NO_ERROR;
+        int skip_initial_sync = 0;
+        int err;
+
+        struct new_c_uuid args;
+
+        memset(&args, 0, sizeof(struct new_c_uuid));
+        if (!new_c_uuid_from_tags(mdev, nlp->tag_list, &args)) {
+                reply->ret_code = ERR_MANDATORY_TAG;
+                return 0;
+        }
+
+        mutex_lock(&mdev->state_mutex); /* Protects us against serialized state changes. */
+
+        if (!get_ldev(mdev)) {
+                retcode = ERR_NO_DISK;
+                goto out;
+        }
+
+        /* this is "skip initial sync", assume to be clean */
+        if (mdev->state.conn == C_CONNECTED && mdev->agreed_pro_version >= 90 &&
+            mdev->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED && args.clear_bm) {
+                dev_info(DEV, "Preparing to skip initial sync\n");
+                skip_initial_sync = 1;
+        } else if (mdev->state.conn != C_STANDALONE) {
+                retcode = ERR_CONNECTED;
+                goto out_dec;
+        }
+
+        drbd_uuid_set(mdev, UI_BITMAP, 0); /* Rotate UI_BITMAP to History 1, etc... */
+        drbd_uuid_new_current(mdev); /* New current, previous to UI_BITMAP */
+
+        if (args.clear_bm) {
+                err = drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write, "clear_n_write from new_c_uuid");
+                if (err) {
+                        dev_err(DEV, "Writing bitmap failed with %d\n",err);
+                        retcode = ERR_IO_MD_DISK;
+                }
+                if (skip_initial_sync) {
+                        drbd_send_uuids_skip_initial_sync(mdev);
+                        _drbd_uuid_set(mdev, UI_BITMAP, 0);
+                        spin_lock_irq(&mdev->req_lock);
+                        _drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
+                                        CS_VERBOSE, NULL);
+                        spin_unlock_irq(&mdev->req_lock);
+                }
+        }
+
+        drbd_md_sync(mdev);
+out_dec:
+        put_ldev(mdev);
+out:
+        mutex_unlock(&mdev->state_mutex);
+
+        reply->ret_code = retcode;
+        return 0;
+}
+
+static struct drbd_conf *ensure_mdev(struct drbd_nl_cfg_req *nlp)
+{
+        struct drbd_conf *mdev;
+
+        if (nlp->drbd_minor >= minor_count)
+                return NULL;
+
+        mdev = minor_to_mdev(nlp->drbd_minor);
+
+        if (!mdev && (nlp->flags & DRBD_NL_CREATE_DEVICE)) {
+                struct gendisk *disk = NULL;
+                mdev = drbd_new_device(nlp->drbd_minor);
+
+                spin_lock_irq(&drbd_pp_lock);
+                if (minor_table[nlp->drbd_minor] == NULL) {
+                        minor_table[nlp->drbd_minor] = mdev;
+                        disk = mdev->vdisk;
+                        mdev = NULL;
+                } /* else: we lost the race */
+                spin_unlock_irq(&drbd_pp_lock);
+
+                if (disk) /* we won the race above */
+                        /* in case we ever add a drbd_delete_device(),
+                         * don't forget the del_gendisk! */
+                        add_disk(disk);
+                else /* we lost the race above */
+                        drbd_free_mdev(mdev);
+
+                mdev = minor_to_mdev(nlp->drbd_minor);
+        }
+
+        return mdev;
+}
+
+struct cn_handler_struct {
+        int (*function)(struct drbd_conf *,
+                         struct drbd_nl_cfg_req *,
+                         struct drbd_nl_cfg_reply *);
+        int reply_body_size;
+};
+
+static struct cn_handler_struct cnd_table[] = {
+        [ P_primary ]           = { &drbd_nl_primary,           0 },
+        [ P_secondary ]         = { &drbd_nl_secondary,         0 },
+        [ P_disk_conf ]         = { &drbd_nl_disk_conf,         0 },
+        [ P_detach ]            = { &drbd_nl_detach,            0 },
+        [ P_net_conf ]          = { &drbd_nl_net_conf,          0 },
+        [ P_disconnect ]        = { &drbd_nl_disconnect,        0 },
+        [ P_resize ]            = { &drbd_nl_resize,            0 },
+        [ P_syncer_conf ]       = { &drbd_nl_syncer_conf,       0 },
+        [ P_invalidate ]        = { &drbd_nl_invalidate,        0 },
+        [ P_invalidate_peer ]   = { &drbd_nl_invalidate_peer,   0 },
+        [ P_pause_sync ]        = { &drbd_nl_pause_sync,        0 },
+        [ P_resume_sync ]       = { &drbd_nl_resume_sync,       0 },
+        [ P_suspend_io ]        = { &drbd_nl_suspend_io,        0 },
+        [ P_resume_io ]         = { &drbd_nl_resume_io,         0 },
+        [ P_outdate ]           = { &drbd_nl_outdate,           0 },
+        [ P_get_config ]        = { &drbd_nl_get_config,
+                                    sizeof(struct syncer_conf_tag_len_struct) +
+                                    sizeof(struct disk_conf_tag_len_struct) +
+                                    sizeof(struct net_conf_tag_len_struct) },
+        [ P_get_state ]         = { &drbd_nl_get_state,
+                                    sizeof(struct get_state_tag_len_struct) +
+                                    sizeof(struct sync_progress_tag_len_struct) },
+        [ P_get_uuids ]         = { &drbd_nl_get_uuids,
+                                    sizeof(struct get_uuids_tag_len_struct) },
+        [ P_get_timeout_flag ]  = { &drbd_nl_get_timeout_flag,
+                                    sizeof(struct get_timeout_flag_tag_len_struct)},
+        [ P_start_ov ]          = { &drbd_nl_start_ov,          0 },
+        [ P_new_c_uuid ]        = { &drbd_nl_new_c_uuid,        0 },
+};
+
+static void drbd_connector_callback(struct cn_msg *req)
+{
+        struct drbd_nl_cfg_req *nlp = (struct drbd_nl_cfg_req *)req->data;
+        struct cn_handler_struct *cm;
+        struct cn_msg *cn_reply;
+        struct drbd_nl_cfg_reply *reply;
+        struct drbd_conf *mdev;
+        int retcode, rr;
+        int reply_size = sizeof(struct cn_msg)
+                + sizeof(struct drbd_nl_cfg_reply)
+                + sizeof(short int);
+
+        if (!try_module_get(THIS_MODULE)) {
+                printk(KERN_ERR "drbd: try_module_get() failed!\n");
+                return;
+        }
+
+        mdev = ensure_mdev(nlp);
+        if (!mdev) {
+                retcode = ERR_MINOR_INVALID;
+                goto fail;
+        }
+
+        trace_drbd_netlink(req, 1);
+
+        if (nlp->packet_type >= P_nl_after_last_packet) {
+                retcode = ERR_PACKET_NR;
+                goto fail;
+        }
+
+        cm = cnd_table + nlp->packet_type;
+
+        /* This may happen if packet number is 0: */
+        if (cm->function == NULL) {
+                retcode = ERR_PACKET_NR;
+                goto fail;
+        }
+
+        reply_size += cm->reply_body_size;
+
+        /* allocation not in the IO path, cqueue thread context */
+        cn_reply = kmalloc(reply_size, GFP_KERNEL);
+        if (!cn_reply) {
+                retcode = ERR_NOMEM;
+                goto fail;
+        }
+        reply = (struct drbd_nl_cfg_reply *) cn_reply->data;
+
+        reply->packet_type =
+                cm->reply_body_size ? nlp->packet_type : P_nl_after_last_packet;
+        reply->minor = nlp->drbd_minor;
+        reply->ret_code = NO_ERROR; /* Might by modified by cm->function. */
+        /* reply->tag_list; might be modified by cm->function. */
+
+        rr = cm->function(mdev, nlp, reply);
+
+        cn_reply->id = req->id;
+        cn_reply->seq = req->seq;
+        cn_reply->ack = req->ack  + 1;
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply) + rr;
+        cn_reply->flags = 0;
+
+        trace_drbd_netlink(cn_reply, 0);
+        rr = cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_KERNEL);
+        if (rr && rr != -ESRCH)
+                printk(KERN_INFO "drbd: cn_netlink_send()=%d\n", rr);
+
+        kfree(cn_reply);
+        module_put(THIS_MODULE);
+        return;
+ fail:
+        drbd_nl_send_reply(req, retcode);
+        module_put(THIS_MODULE);
+}
+
+static atomic_t drbd_nl_seq = ATOMIC_INIT(2); /* two. */
+
+static unsigned short *
+__tl_add_blob(unsigned short *tl, enum drbd_tags tag, const void *data,
+        unsigned short len, int nul_terminated)
+{
+        unsigned short l = tag_descriptions[tag_number(tag)].max_len;
+        len = (len < l) ? len :  l;
+        put_unaligned(tag, tl++);
+        put_unaligned(len, tl++);
+        memcpy(tl, data, len);
+        tl = (unsigned short*)((char*)tl + len);
+        if (nul_terminated)
+                *((char*)tl - 1) = 0;
+        return tl;
+}
+
+static unsigned short *
+tl_add_blob(unsigned short *tl, enum drbd_tags tag, const void *data, int len)
+{
+        return __tl_add_blob(tl, tag, data, len, 0);
+}
+
+static unsigned short *
+tl_add_str(unsigned short *tl, enum drbd_tags tag, const char *str)
+{
+        return __tl_add_blob(tl, tag, str, strlen(str)+1, 0);
+}
+
+static unsigned short *
+tl_add_int(unsigned short *tl, enum drbd_tags tag, const void *val)
+{
+        put_unaligned(tag, tl++);
+        switch(tag_type(tag)) {
+        case TT_INTEGER:
+                put_unaligned(sizeof(int), tl++);
+                put_unaligned(*(int *)val, (int *)tl);
+                tl = (unsigned short*)((char*)tl+sizeof(int));
+                break;
+        case TT_INT64:
+                put_unaligned(sizeof(u64), tl++);
+                put_unaligned(*(u64 *)val, (u64 *)tl);
+                tl = (unsigned short*)((char*)tl+sizeof(u64));
+                break;
+        default:
+                /* someone did something stupid. */
+                ;
+        }
+        return tl;
+}
+
+void drbd_bcast_state(struct drbd_conf *mdev, union drbd_state state)
+{
+        char buffer[sizeof(struct cn_msg)+
+                    sizeof(struct drbd_nl_cfg_reply)+
+                    sizeof(struct get_state_tag_len_struct)+
+                    sizeof(short int)];
+        struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+        struct drbd_nl_cfg_reply *reply =
+                (struct drbd_nl_cfg_reply *)cn_reply->data;
+        unsigned short *tl = reply->tag_list;
+
+        /* dev_warn(DEV, "drbd_bcast_state() got called\n"); */
+
+        tl = get_state_to_tags(mdev, (struct get_state *)&state, tl);
+
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        cn_reply->id.idx = CN_IDX_DRBD;
+        cn_reply->id.val = CN_VAL_DRBD;
+
+        cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+        cn_reply->ack = 0; /* not used here. */
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+                (int)((char *)tl - (char *)reply->tag_list);
+        cn_reply->flags = 0;
+
+        reply->packet_type = P_get_state;
+        reply->minor = mdev_to_minor(mdev);
+        reply->ret_code = NO_ERROR;
+
+        trace_drbd_netlink(cn_reply, 0);
+        cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+void drbd_bcast_ev_helper(struct drbd_conf *mdev, char *helper_name)
+{
+        char buffer[sizeof(struct cn_msg)+
+                    sizeof(struct drbd_nl_cfg_reply)+
+                    sizeof(struct call_helper_tag_len_struct)+
+                    sizeof(short int)];
+        struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+        struct drbd_nl_cfg_reply *reply =
+                (struct drbd_nl_cfg_reply *)cn_reply->data;
+        unsigned short *tl = reply->tag_list;
+
+        /* dev_warn(DEV, "drbd_bcast_state() got called\n"); */
+
+        tl = tl_add_str(tl, T_helper, helper_name);
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        cn_reply->id.idx = CN_IDX_DRBD;
+        cn_reply->id.val = CN_VAL_DRBD;
+
+        cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+        cn_reply->ack = 0; /* not used here. */
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+                (int)((char *)tl - (char *)reply->tag_list);
+        cn_reply->flags = 0;
+
+        reply->packet_type = P_call_helper;
+        reply->minor = mdev_to_minor(mdev);
+        reply->ret_code = NO_ERROR;
+
+        trace_drbd_netlink(cn_reply, 0);
+        cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+void drbd_bcast_ee(struct drbd_conf *mdev,
+                const char *reason, const int dgs,
+                const char* seen_hash, const char* calc_hash,
+                const struct drbd_epoch_entry* e)
+{
+        struct cn_msg *cn_reply;
+        struct drbd_nl_cfg_reply *reply;
+        struct bio_vec *bvec;
+        unsigned short *tl;
+        int i;
+
+        if (!e)
+                return;
+        if (!reason || !reason[0])
+                return;
+
+        /* apparently we have to memcpy twice, first to prepare the data for the
+         * struct cn_msg, then within cn_netlink_send from the cn_msg to the
+         * netlink skb. */
+        /* receiver thread context, which is not in the writeout path (of this node),
+         * but may be in the writeout path of the _other_ node.
+         * GFP_NOIO to avoid potential "distributed deadlock". */
+        cn_reply = kmalloc(
+                sizeof(struct cn_msg)+
+                sizeof(struct drbd_nl_cfg_reply)+
+                sizeof(struct dump_ee_tag_len_struct)+
+                sizeof(short int),
+                GFP_NOIO);
+
+        if (!cn_reply) {
+                dev_err(DEV, "could not kmalloc buffer for drbd_bcast_ee, sector %llu, size %u\n",
+                                (unsigned long long)e->sector, e->size);
+                return;
+        }
+
+        reply = (struct drbd_nl_cfg_reply*)cn_reply->data;
+        tl = reply->tag_list;
+
+        tl = tl_add_str(tl, T_dump_ee_reason, reason);
+        tl = tl_add_blob(tl, T_seen_digest, seen_hash, dgs);
+        tl = tl_add_blob(tl, T_calc_digest, calc_hash, dgs);
+        tl = tl_add_int(tl, T_ee_sector, &e->sector);
+        tl = tl_add_int(tl, T_ee_block_id, &e->block_id);
+
+        put_unaligned(T_ee_data, tl++);
+        put_unaligned(e->size, tl++);
+
+        __bio_for_each_segment(bvec, e->private_bio, i, 0) {
+                void *d = kmap(bvec->bv_page);
+                memcpy(tl, d + bvec->bv_offset, bvec->bv_len);
+                kunmap(bvec->bv_page);
+                tl=(unsigned short*)((char*)tl + bvec->bv_len);
+        }
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        cn_reply->id.idx = CN_IDX_DRBD;
+        cn_reply->id.val = CN_VAL_DRBD;
+
+        cn_reply->seq = atomic_add_return(1,&drbd_nl_seq);
+        cn_reply->ack = 0; // not used here.
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+                (int)((char*)tl - (char*)reply->tag_list);
+        cn_reply->flags = 0;
+
+        reply->packet_type = P_dump_ee;
+        reply->minor = mdev_to_minor(mdev);
+        reply->ret_code = NO_ERROR;
+
+        trace_drbd_netlink(cn_reply, 0);
+        cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+        kfree(cn_reply);
+}
+
+void drbd_bcast_sync_progress(struct drbd_conf *mdev)
+{
+        char buffer[sizeof(struct cn_msg)+
+                    sizeof(struct drbd_nl_cfg_reply)+
+                    sizeof(struct sync_progress_tag_len_struct)+
+                    sizeof(short int)];
+        struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+        struct drbd_nl_cfg_reply *reply =
+                (struct drbd_nl_cfg_reply *)cn_reply->data;
+        unsigned short *tl = reply->tag_list;
+        unsigned long rs_left;
+        unsigned int res;
+
+        /* no local ref, no bitmap, no syncer progress, no broadcast. */
+        if (!get_ldev(mdev))
+                return;
+        drbd_get_syncer_progress(mdev, &rs_left, &res);
+        put_ldev(mdev);
+
+        tl = tl_add_int(tl, T_sync_progress, &res);
+        put_unaligned(TT_END, tl++); /* Close the tag list */
+
+        cn_reply->id.idx = CN_IDX_DRBD;
+        cn_reply->id.val = CN_VAL_DRBD;
+
+        cn_reply->seq = atomic_add_return(1, &drbd_nl_seq);
+        cn_reply->ack = 0; /* not used here. */
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply) +
+                (int)((char *)tl - (char *)reply->tag_list);
+        cn_reply->flags = 0;
+
+        reply->packet_type = P_sync_progress;
+        reply->minor = mdev_to_minor(mdev);
+        reply->ret_code = NO_ERROR;
+
+        trace_drbd_netlink(cn_reply, 0);
+        cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+}
+
+int __init drbd_nl_init(void)
+{
+        static struct cb_id cn_id_drbd;
+        int err, try=10;
+
+        cn_id_drbd.val = CN_VAL_DRBD;
+        do {
+                cn_id_drbd.idx = cn_idx;
+                err = cn_add_callback(&cn_id_drbd, "cn_drbd", &drbd_connector_callback);
+                if (!err)
+                        break;
+                cn_idx = (cn_idx + CN_IDX_STEP);
+        } while (try--);
+
+        if (err) {
+                printk(KERN_ERR "drbd: cn_drbd failed to register\n");
+                return err;
+        }
+
+        return 0;
+}
+
+void drbd_nl_cleanup(void)
+{
+        static struct cb_id cn_id_drbd;
+
+        cn_id_drbd.idx = cn_idx;
+        cn_id_drbd.val = CN_VAL_DRBD;
+
+        cn_del_callback(&cn_id_drbd);
+}
+
+void drbd_nl_send_reply(struct cn_msg *req, int ret_code)
+{
+        char buffer[sizeof(struct cn_msg)+sizeof(struct drbd_nl_cfg_reply)];
+        struct cn_msg *cn_reply = (struct cn_msg *) buffer;
+        struct drbd_nl_cfg_reply *reply =
+                (struct drbd_nl_cfg_reply *)cn_reply->data;
+        int rr;
+
+        cn_reply->id = req->id;
+
+        cn_reply->seq = req->seq;
+        cn_reply->ack = req->ack  + 1;
+        cn_reply->len = sizeof(struct drbd_nl_cfg_reply);
+        cn_reply->flags = 0;
+
+        reply->minor = ((struct drbd_nl_cfg_req *)req->data)->drbd_minor;
+        reply->ret_code = ret_code;
+
+        trace_drbd_netlink(cn_reply, 0);
+        rr = cn_netlink_send(cn_reply, CN_IDX_DRBD, GFP_NOIO);
+        if (rr && rr != -ESRCH)
+                printk(KERN_INFO "drbd: cn_netlink_send()=%d\n", rr);
+}
+
diff --git a/drivers/block/drbd/drbd_proc.c b/drivers/block/drbd/drbd_proc.c
new file mode 100644
index 000000000000..98fcb7450c76
--- /dev/null
+++ b/drivers/block/drbd/drbd_proc.c
@@ -0,0 +1,266 @@
+/*
+   drbd_proc.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/slab.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+
+static int drbd_proc_open(struct inode *inode, struct file *file);
+
+
+struct proc_dir_entry *drbd_proc;
+struct file_operations drbd_proc_fops = {
+        .owner          = THIS_MODULE,
+        .open           = drbd_proc_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
+
+/*lge
+ * progress bars shamelessly adapted from driver/md/md.c
+ * output looks like
+ *      [=====>..............] 33.5% (23456/123456)
+ *      finish: 2:20:20 speed: 6,345 (6,456) K/sec
+ */
+static void drbd_syncer_progress(struct drbd_conf *mdev, struct seq_file *seq)
+{
+        unsigned long db, dt, dbdt, rt, rs_left;
+        unsigned int res;
+        int i, x, y;
+
+        drbd_get_syncer_progress(mdev, &rs_left, &res);
+
+        x = res/50;
+        y = 20-x;
+        seq_printf(seq, "\t[");
+        for (i = 1; i < x; i++)
+                seq_printf(seq, "=");
+        seq_printf(seq, ">");
+        for (i = 0; i < y; i++)
+                seq_printf(seq, ".");
+        seq_printf(seq, "] ");
+
+        seq_printf(seq, "sync'ed:%3u.%u%% ", res / 10, res % 10);
+        /* if more than 1 GB display in MB */
+        if (mdev->rs_total > 0x100000L)
+                seq_printf(seq, "(%lu/%lu)M\n\t",
+                            (unsigned long) Bit2KB(rs_left >> 10),
+                            (unsigned long) Bit2KB(mdev->rs_total >> 10));
+        else
+                seq_printf(seq, "(%lu/%lu)K\n\t",
+                            (unsigned long) Bit2KB(rs_left),
+                            (unsigned long) Bit2KB(mdev->rs_total));
+
+        /* see drivers/md/md.c
+         * We do not want to overflow, so the order of operands and
+         * the * 100 / 100 trick are important. We do a +1 to be
+         * safe against division by zero. We only estimate anyway.
+         *
+         * dt: time from mark until now
+         * db: blocks written from mark until now
+         * rt: remaining time
+         */
+        dt = (jiffies - mdev->rs_mark_time) / HZ;
+
+        if (dt > 20) {
+                /* if we made no update to rs_mark_time for too long,
+                 * we are stalled. show that. */
+                seq_printf(seq, "stalled\n");
+                return;
+        }
+
+        if (!dt)
+                dt++;
+        db = mdev->rs_mark_left - rs_left;
+        rt = (dt * (rs_left / (db/100+1)))/100; /* seconds */
+
+        seq_printf(seq, "finish: %lu:%02lu:%02lu",
+                rt / 3600, (rt % 3600) / 60, rt % 60);
+
+        /* current speed average over (SYNC_MARKS * SYNC_MARK_STEP) jiffies */
+        dbdt = Bit2KB(db/dt);
+        if (dbdt > 1000)
+                seq_printf(seq, " speed: %ld,%03ld",
+                        dbdt/1000, dbdt % 1000);
+        else
+                seq_printf(seq, " speed: %ld", dbdt);
+
+        /* mean speed since syncer started
+         * we do account for PausedSync periods */
+        dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
+        if (dt <= 0)
+                dt = 1;
+        db = mdev->rs_total - rs_left;
+        dbdt = Bit2KB(db/dt);
+        if (dbdt > 1000)
+                seq_printf(seq, " (%ld,%03ld)",
+                        dbdt/1000, dbdt % 1000);
+        else
+                seq_printf(seq, " (%ld)", dbdt);
+
+        seq_printf(seq, " K/sec\n");
+}
+
+static void resync_dump_detail(struct seq_file *seq, struct lc_element *e)
+{
+        struct bm_extent *bme = lc_entry(e, struct bm_extent, lce);
+
+        seq_printf(seq, "%5d %s %s\n", bme->rs_left,
+                   bme->flags & BME_NO_WRITES ? "NO_WRITES" : "---------",
+                   bme->flags & BME_LOCKED ? "LOCKED" : "------"
+                   );
+}
+
+static int drbd_seq_show(struct seq_file *seq, void *v)
+{
+        int i, hole = 0;
+        const char *sn;
+        struct drbd_conf *mdev;
+
+        static char write_ordering_chars[] = {
+                [WO_none] = 'n',
+                [WO_drain_io] = 'd',
+                [WO_bdev_flush] = 'f',
+                [WO_bio_barrier] = 'b',
+        };
+
+        seq_printf(seq, "version: " REL_VERSION " (api:%d/proto:%d-%d)\n%s\n",
+                   API_VERSION, PRO_VERSION_MIN, PRO_VERSION_MAX, drbd_buildtag());
+
+        /*
+          cs .. connection state
+          ro .. node role (local/remote)
+          ds .. disk state (local/remote)
+             protocol
+             various flags
+          ns .. network send
+          nr .. network receive
+          dw .. disk write
+          dr .. disk read
+          al .. activity log write count
+          bm .. bitmap update write count
+          pe .. pending (waiting for ack or data reply)
+          ua .. unack'd (still need to send ack or data reply)
+          ap .. application requests accepted, but not yet completed
+          ep .. number of epochs currently "on the fly", P_BARRIER_ACK pending
+          wo .. write ordering mode currently in use
+         oos .. known out-of-sync kB
+        */
+
+        for (i = 0; i < minor_count; i++) {
+                mdev = minor_to_mdev(i);
+                if (!mdev) {
+                        hole = 1;
+                        continue;
+                }
+                if (hole) {
+                        hole = 0;
+                        seq_printf(seq, "\n");
+                }
+
+                sn = drbd_conn_str(mdev->state.conn);
+
+                if (mdev->state.conn == C_STANDALONE &&
+                    mdev->state.disk == D_DISKLESS &&
+                    mdev->state.role == R_SECONDARY) {
+                        seq_printf(seq, "%2d: cs:Unconfigured\n", i);
+                } else {
+                        seq_printf(seq,
+                           "%2d: cs:%s ro:%s/%s ds:%s/%s %c %c%c%c%c%c\n"
+                           "    ns:%u nr:%u dw:%u dr:%u al:%u bm:%u "
+                           "lo:%d pe:%d ua:%d ap:%d ep:%d wo:%c",
+                           i, sn,
+                           drbd_role_str(mdev->state.role),
+                           drbd_role_str(mdev->state.peer),
+                           drbd_disk_str(mdev->state.disk),
+                           drbd_disk_str(mdev->state.pdsk),
+                           (mdev->net_conf == NULL ? ' ' :
+                            (mdev->net_conf->wire_protocol - DRBD_PROT_A+'A')),
+                           mdev->state.susp ? 's' : 'r',
+                           mdev->state.aftr_isp ? 'a' : '-',
+                           mdev->state.peer_isp ? 'p' : '-',
+                           mdev->state.user_isp ? 'u' : '-',
+                           mdev->congestion_reason ?: '-',
+                           mdev->send_cnt/2,
+                           mdev->recv_cnt/2,
+                           mdev->writ_cnt/2,
+                           mdev->read_cnt/2,
+                           mdev->al_writ_cnt,
+                           mdev->bm_writ_cnt,
+                           atomic_read(&mdev->local_cnt),
+                           atomic_read(&mdev->ap_pending_cnt) +
+                           atomic_read(&mdev->rs_pending_cnt),
+                           atomic_read(&mdev->unacked_cnt),
+                           atomic_read(&mdev->ap_bio_cnt),
+                           mdev->epochs,
+                           write_ordering_chars[mdev->write_ordering]
+                        );
+                        seq_printf(seq, " oos:%lu\n",
+                                   Bit2KB(drbd_bm_total_weight(mdev)));
+                }
+                if (mdev->state.conn == C_SYNC_SOURCE ||
+                    mdev->state.conn == C_SYNC_TARGET)
+                        drbd_syncer_progress(mdev, seq);
+
+                if (mdev->state.conn == C_VERIFY_S || mdev->state.conn == C_VERIFY_T)
+                        seq_printf(seq, "\t%3d%%      %lu/%lu\n",
+                                   (int)((mdev->rs_total-mdev->ov_left) /
+                                         (mdev->rs_total/100+1)),
+                                   mdev->rs_total - mdev->ov_left,
+                                   mdev->rs_total);
+
+                if (proc_details >= 1 && get_ldev_if_state(mdev, D_FAILED)) {
+                        lc_seq_printf_stats(seq, mdev->resync);
+                        lc_seq_printf_stats(seq, mdev->act_log);
+                        put_ldev(mdev);
+                }
+
+                if (proc_details >= 2) {
+                        if (mdev->resync) {
+                                lc_seq_dump_details(seq, mdev->resync, "rs_left",
+                                        resync_dump_detail);
+                        }
+                }
+        }
+
+        return 0;
+}
+
+static int drbd_proc_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, drbd_seq_show, PDE(inode)->data);
+}
+
+/* PROC FS stuff end */
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
new file mode 100644
index 000000000000..63686c4d85cf
--- /dev/null
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -0,0 +1,4456 @@
+/*
+   drbd_receiver.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <asm/uaccess.h>
+#include <net/sock.h>
+
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/in.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/smp_lock.h>
+#include <linux/pkt_sched.h>
+#define __KERNEL_SYSCALLS__
+#include <linux/unistd.h>
+#include <linux/vmalloc.h>
+#include <linux/random.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/scatterlist.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h"
+
+#include "drbd_vli.h"
+
+struct flush_work {
+        struct drbd_work w;
+        struct drbd_epoch *epoch;
+};
+
+enum finish_epoch {
+        FE_STILL_LIVE,
+        FE_DESTROYED,
+        FE_RECYCLED,
+};
+
+static int drbd_do_handshake(struct drbd_conf *mdev);
+static int drbd_do_auth(struct drbd_conf *mdev);
+
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *, struct drbd_epoch *, enum epoch_event);
+static int e_end_block(struct drbd_conf *, struct drbd_work *, int);
+
+static struct drbd_epoch *previous_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch)
+{
+        struct drbd_epoch *prev;
+        spin_lock(&mdev->epoch_lock);
+        prev = list_entry(epoch->list.prev, struct drbd_epoch, list);
+        if (prev == epoch || prev == mdev->current_epoch)
+                prev = NULL;
+        spin_unlock(&mdev->epoch_lock);
+        return prev;
+}
+
+#define GFP_TRY (__GFP_HIGHMEM | __GFP_NOWARN)
+
+static struct page *drbd_pp_first_page_or_try_alloc(struct drbd_conf *mdev)
+{
+        struct page *page = NULL;
+
+        /* Yes, testing drbd_pp_vacant outside the lock is racy.
+         * So what. It saves a spin_lock. */
+        if (drbd_pp_vacant > 0) {
+                spin_lock(&drbd_pp_lock);
+                page = drbd_pp_pool;
+                if (page) {
+                        drbd_pp_pool = (struct page *)page_private(page);
+                        set_page_private(page, 0); /* just to be polite */
+                        drbd_pp_vacant--;
+                }
+                spin_unlock(&drbd_pp_lock);
+        }
+        /* GFP_TRY, because we must not cause arbitrary write-out: in a DRBD
+         * "criss-cross" setup, that might cause write-out on some other DRBD,
+         * which in turn might block on the other node at this very place.  */
+        if (!page)
+                page = alloc_page(GFP_TRY);
+        if (page)
+                atomic_inc(&mdev->pp_in_use);
+        return page;
+}
+
+/* kick lower level device, if we have more than (arbitrary number)
+ * reference counts on it, which typically are locally submitted io
+ * requests.  don't use unacked_cnt, so we speed up proto A and B, too. */
+static void maybe_kick_lo(struct drbd_conf *mdev)
+{
+        if (atomic_read(&mdev->local_cnt) >= mdev->net_conf->unplug_watermark)
+                drbd_kick_lo(mdev);
+}
+
+static void reclaim_net_ee(struct drbd_conf *mdev, struct list_head *to_be_freed)
+{
+        struct drbd_epoch_entry *e;
+        struct list_head *le, *tle;
+
+        /* The EEs are always appended to the end of the list. Since
+           they are sent in order over the wire, they have to finish
+           in order. As soon as we see the first not finished we can
+           stop to examine the list... */
+
+        list_for_each_safe(le, tle, &mdev->net_ee) {
+                e = list_entry(le, struct drbd_epoch_entry, w.list);
+                if (drbd_bio_has_active_page(e->private_bio))
+                        break;
+                list_move(le, to_be_freed);
+        }
+}
+
+static void drbd_kick_lo_and_reclaim_net(struct drbd_conf *mdev)
+{
+        LIST_HEAD(reclaimed);
+        struct drbd_epoch_entry *e, *t;
+
+        maybe_kick_lo(mdev);
+        spin_lock_irq(&mdev->req_lock);
+        reclaim_net_ee(mdev, &reclaimed);
+        spin_unlock_irq(&mdev->req_lock);
+
+        list_for_each_entry_safe(e, t, &reclaimed, w.list)
+                drbd_free_ee(mdev, e);
+}
+
+/**
+ * drbd_pp_alloc() - Returns a page, fails only if a signal comes in
+ * @mdev:       DRBD device.
+ * @retry:      whether or not to retry allocation forever (or until signalled)
+ *
+ * Tries to allocate a page, first from our own page pool, then from the
+ * kernel, unless this allocation would exceed the max_buffers setting.
+ * If @retry is non-zero, retry until DRBD frees a page somewhere else.
+ */
+static struct page *drbd_pp_alloc(struct drbd_conf *mdev, int retry)
+{
+        struct page *page = NULL;
+        DEFINE_WAIT(wait);
+
+        if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
+                page = drbd_pp_first_page_or_try_alloc(mdev);
+                if (page)
+                        return page;
+        }
+
+        for (;;) {
+                prepare_to_wait(&drbd_pp_wait, &wait, TASK_INTERRUPTIBLE);
+
+                drbd_kick_lo_and_reclaim_net(mdev);
+
+                if (atomic_read(&mdev->pp_in_use) < mdev->net_conf->max_buffers) {
+                        page = drbd_pp_first_page_or_try_alloc(mdev);
+                        if (page)
+                                break;
+                }
+
+                if (!retry)
+                        break;
+
+                if (signal_pending(current)) {
+                        dev_warn(DEV, "drbd_pp_alloc interrupted!\n");
+                        break;
+                }
+
+                schedule();
+        }
+        finish_wait(&drbd_pp_wait, &wait);
+
+        return page;
+}
+
+/* Must not be used from irq, as that may deadlock: see drbd_pp_alloc.
+ * Is also used from inside an other spin_lock_irq(&mdev->req_lock) */
+static void drbd_pp_free(struct drbd_conf *mdev, struct page *page)
+{
+        int free_it;
+
+        spin_lock(&drbd_pp_lock);
+        if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
+                free_it = 1;
+        } else {
+                set_page_private(page, (unsigned long)drbd_pp_pool);
+                drbd_pp_pool = page;
+                drbd_pp_vacant++;
+                free_it = 0;
+        }
+        spin_unlock(&drbd_pp_lock);
+
+        atomic_dec(&mdev->pp_in_use);
+
+        if (free_it)
+                __free_page(page);
+
+        wake_up(&drbd_pp_wait);
+}
+
+static void drbd_pp_free_bio_pages(struct drbd_conf *mdev, struct bio *bio)
+{
+        struct page *p_to_be_freed = NULL;
+        struct page *page;
+        struct bio_vec *bvec;
+        int i;
+
+        spin_lock(&drbd_pp_lock);
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                if (drbd_pp_vacant > (DRBD_MAX_SEGMENT_SIZE/PAGE_SIZE)*minor_count) {
+                        set_page_private(bvec->bv_page, (unsigned long)p_to_be_freed);
+                        p_to_be_freed = bvec->bv_page;
+                } else {
+                        set_page_private(bvec->bv_page, (unsigned long)drbd_pp_pool);
+                        drbd_pp_pool = bvec->bv_page;
+                        drbd_pp_vacant++;
+                }
+        }
+        spin_unlock(&drbd_pp_lock);
+        atomic_sub(bio->bi_vcnt, &mdev->pp_in_use);
+
+        while (p_to_be_freed) {
+                page = p_to_be_freed;
+                p_to_be_freed = (struct page *)page_private(page);
+                set_page_private(page, 0); /* just to be polite */
+                put_page(page);
+        }
+
+        wake_up(&drbd_pp_wait);
+}
+
+/*
+You need to hold the req_lock:
+ _drbd_wait_ee_list_empty()
+
+You must not have the req_lock:
+ drbd_free_ee()
+ drbd_alloc_ee()
+ drbd_init_ee()
+ drbd_release_ee()
+ drbd_ee_fix_bhs()
+ drbd_process_done_ee()
+ drbd_clear_done_ee()
+ drbd_wait_ee_list_empty()
+*/
+
+struct drbd_epoch_entry *drbd_alloc_ee(struct drbd_conf *mdev,
+                                     u64 id,
+                                     sector_t sector,
+                                     unsigned int data_size,
+                                     gfp_t gfp_mask) __must_hold(local)
+{
+        struct request_queue *q;
+        struct drbd_epoch_entry *e;
+        struct page *page;
+        struct bio *bio;
+        unsigned int ds;
+
+        if (FAULT_ACTIVE(mdev, DRBD_FAULT_AL_EE))
+                return NULL;
+
+        e = mempool_alloc(drbd_ee_mempool, gfp_mask & ~__GFP_HIGHMEM);
+        if (!e) {
+                if (!(gfp_mask & __GFP_NOWARN))
+                        dev_err(DEV, "alloc_ee: Allocation of an EE failed\n");
+                return NULL;
+        }
+
+        bio = bio_alloc(gfp_mask & ~__GFP_HIGHMEM, div_ceil(data_size, PAGE_SIZE));
+        if (!bio) {
+                if (!(gfp_mask & __GFP_NOWARN))
+                        dev_err(DEV, "alloc_ee: Allocation of a bio failed\n");
+                goto fail1;
+        }
+
+        bio->bi_bdev = mdev->ldev->backing_bdev;
+        bio->bi_sector = sector;
+
+        ds = data_size;
+        while (ds) {
+                page = drbd_pp_alloc(mdev, (gfp_mask & __GFP_WAIT));
+                if (!page) {
+                        if (!(gfp_mask & __GFP_NOWARN))
+                                dev_err(DEV, "alloc_ee: Allocation of a page failed\n");
+                        goto fail2;
+                }
+                if (!bio_add_page(bio, page, min_t(int, ds, PAGE_SIZE), 0)) {
+                        drbd_pp_free(mdev, page);
+                        dev_err(DEV, "alloc_ee: bio_add_page(s=%llu,"
+                            "data_size=%u,ds=%u) failed\n",
+                            (unsigned long long)sector, data_size, ds);
+
+                        q = bdev_get_queue(bio->bi_bdev);
+                        if (q->merge_bvec_fn) {
+                                struct bvec_merge_data bvm = {
+                                        .bi_bdev = bio->bi_bdev,
+                                        .bi_sector = bio->bi_sector,
+                                        .bi_size = bio->bi_size,
+                                        .bi_rw = bio->bi_rw,
+                                };
+                                int l = q->merge_bvec_fn(q, &bvm,
+                                                &bio->bi_io_vec[bio->bi_vcnt]);
+                                dev_err(DEV, "merge_bvec_fn() = %d\n", l);
+                        }
+
+                        /* dump more of the bio. */
+                        dev_err(DEV, "bio->bi_max_vecs = %d\n", bio->bi_max_vecs);
+                        dev_err(DEV, "bio->bi_vcnt = %d\n", bio->bi_vcnt);
+                        dev_err(DEV, "bio->bi_size = %d\n", bio->bi_size);
+                        dev_err(DEV, "bio->bi_phys_segments = %d\n", bio->bi_phys_segments);
+
+                        goto fail2;
+                        break;
+                }
+                ds -= min_t(int, ds, PAGE_SIZE);
+        }
+
+        D_ASSERT(data_size == bio->bi_size);
+
+        bio->bi_private = e;
+        e->mdev = mdev;
+        e->sector = sector;
+        e->size = bio->bi_size;
+
+        e->private_bio = bio;
+        e->block_id = id;
+        INIT_HLIST_NODE(&e->colision);
+        e->epoch = NULL;
+        e->flags = 0;
+
+        trace_drbd_ee(mdev, e, "allocated");
+
+        return e;
+
+ fail2:
+        drbd_pp_free_bio_pages(mdev, bio);
+        bio_put(bio);
+ fail1:
+        mempool_free(e, drbd_ee_mempool);
+
+        return NULL;
+}
+
+void drbd_free_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+        struct bio *bio = e->private_bio;
+        trace_drbd_ee(mdev, e, "freed");
+        drbd_pp_free_bio_pages(mdev, bio);
+        bio_put(bio);
+        D_ASSERT(hlist_unhashed(&e->colision));
+        mempool_free(e, drbd_ee_mempool);
+}
+
+int drbd_release_ee(struct drbd_conf *mdev, struct list_head *list)
+{
+        LIST_HEAD(work_list);
+        struct drbd_epoch_entry *e, *t;
+        int count = 0;
+
+        spin_lock_irq(&mdev->req_lock);
+        list_splice_init(list, &work_list);
+        spin_unlock_irq(&mdev->req_lock);
+
+        list_for_each_entry_safe(e, t, &work_list, w.list) {
+                drbd_free_ee(mdev, e);
+                count++;
+        }
+        return count;
+}
+
+
+/*
+ * This function is called from _asender only_
+ * but see also comments in _req_mod(,barrier_acked)
+ * and receive_Barrier.
+ *
+ * Move entries from net_ee to done_ee, if ready.
+ * Grab done_ee, call all callbacks, free the entries.
+ * The callbacks typically send out ACKs.
+ */
+static int drbd_process_done_ee(struct drbd_conf *mdev)
+{
+        LIST_HEAD(work_list);
+        LIST_HEAD(reclaimed);
+        struct drbd_epoch_entry *e, *t;
+        int ok = (mdev->state.conn >= C_WF_REPORT_PARAMS);
+
+        spin_lock_irq(&mdev->req_lock);
+        reclaim_net_ee(mdev, &reclaimed);
+        list_splice_init(&mdev->done_ee, &work_list);
+        spin_unlock_irq(&mdev->req_lock);
+
+        list_for_each_entry_safe(e, t, &reclaimed, w.list)
+                drbd_free_ee(mdev, e);
+
+        /* possible callbacks here:
+         * e_end_block, and e_end_resync_block, e_send_discard_ack.
+         * all ignore the last argument.
+         */
+        list_for_each_entry_safe(e, t, &work_list, w.list) {
+                trace_drbd_ee(mdev, e, "process_done_ee");
+                /* list_del not necessary, next/prev members not touched */
+                ok = e->w.cb(mdev, &e->w, !ok) && ok;
+                drbd_free_ee(mdev, e);
+        }
+        wake_up(&mdev->ee_wait);
+
+        return ok;
+}
+
+void _drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+        DEFINE_WAIT(wait);
+
+        /* avoids spin_lock/unlock
+         * and calling prepare_to_wait in the fast path */
+        while (!list_empty(head)) {
+                prepare_to_wait(&mdev->ee_wait, &wait, TASK_UNINTERRUPTIBLE);
+                spin_unlock_irq(&mdev->req_lock);
+                drbd_kick_lo(mdev);
+                schedule();
+                finish_wait(&mdev->ee_wait, &wait);
+                spin_lock_irq(&mdev->req_lock);
+        }
+}
+
+void drbd_wait_ee_list_empty(struct drbd_conf *mdev, struct list_head *head)
+{
+        spin_lock_irq(&mdev->req_lock);
+        _drbd_wait_ee_list_empty(mdev, head);
+        spin_unlock_irq(&mdev->req_lock);
+}
+
+/* see also kernel_accept; which is only present since 2.6.18.
+ * also we want to log which part of it failed, exactly */
+static int drbd_accept(struct drbd_conf *mdev, const char **what,
+                struct socket *sock, struct socket **newsock)
+{
+        struct sock *sk = sock->sk;
+        int err = 0;
+
+        *what = "listen";
+        err = sock->ops->listen(sock, 5);
+        if (err < 0)
+                goto out;
+
+        *what = "sock_create_lite";
+        err = sock_create_lite(sk->sk_family, sk->sk_type, sk->sk_protocol,
+                               newsock);
+        if (err < 0)
+                goto out;
+
+        *what = "accept";
+        err = sock->ops->accept(sock, *newsock, 0);
+        if (err < 0) {
+                sock_release(*newsock);
+                *newsock = NULL;
+                goto out;
+        }
+        (*newsock)->ops  = sock->ops;
+
+out:
+        return err;
+}
+
+static int drbd_recv_short(struct drbd_conf *mdev, struct socket *sock,
+                    void *buf, size_t size, int flags)
+{
+        mm_segment_t oldfs;
+        struct kvec iov = {
+                .iov_base = buf,
+                .iov_len = size,
+        };
+        struct msghdr msg = {
+                .msg_iovlen = 1,
+                .msg_iov = (struct iovec *)&iov,
+                .msg_flags = (flags ? flags : MSG_WAITALL | MSG_NOSIGNAL)
+        };
+        int rv;
+
+        oldfs = get_fs();
+        set_fs(KERNEL_DS);
+        rv = sock_recvmsg(sock, &msg, size, msg.msg_flags);
+        set_fs(oldfs);
+
+        return rv;
+}
+
+static int drbd_recv(struct drbd_conf *mdev, void *buf, size_t size)
+{
+        mm_segment_t oldfs;
+        struct kvec iov = {
+                .iov_base = buf,
+                .iov_len = size,
+        };
+        struct msghdr msg = {
+                .msg_iovlen = 1,
+                .msg_iov = (struct iovec *)&iov,
+                .msg_flags = MSG_WAITALL | MSG_NOSIGNAL
+        };
+        int rv;
+
+        oldfs = get_fs();
+        set_fs(KERNEL_DS);
+
+        for (;;) {
+                rv = sock_recvmsg(mdev->data.socket, &msg, size, msg.msg_flags);
+                if (rv == size)
+                        break;
+
+                /* Note:
+                 * ECONNRESET   other side closed the connection
+                 * ERESTARTSYS  (on  sock) we got a signal
+                 */
+
+                if (rv < 0) {
+                        if (rv == -ECONNRESET)
+                                dev_info(DEV, "sock was reset by peer\n");
+                        else if (rv != -ERESTARTSYS)
+                                dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+                        break;
+                } else if (rv == 0) {
+                        dev_info(DEV, "sock was shut down by peer\n");
+                        break;
+                } else  {
+                        /* signal came in, or peer/link went down,
+                         * after we read a partial message
+                         */
+                        /* D_ASSERT(signal_pending(current)); */
+                        break;
+                }
+        };
+
+        set_fs(oldfs);
+
+        if (rv != size)
+                drbd_force_state(mdev, NS(conn, C_BROKEN_PIPE));
+
+        return rv;
+}
+
+static struct socket *drbd_try_connect(struct drbd_conf *mdev)
+{
+        const char *what;
+        struct socket *sock;
+        struct sockaddr_in6 src_in6;
+        int err;
+        int disconnect_on_error = 1;
+
+        if (!get_net_conf(mdev))
+                return NULL;
+
+        what = "sock_create_kern";
+        err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+                SOCK_STREAM, IPPROTO_TCP, &sock);
+        if (err < 0) {
+                sock = NULL;
+                goto out;
+        }
+
+        sock->sk->sk_rcvtimeo =
+        sock->sk->sk_sndtimeo =  mdev->net_conf->try_connect_int*HZ;
+
+       /* explicitly bind to the configured IP as source IP
+        *  for the outgoing connections.
+        *  This is needed for multihomed hosts and to be
+        *  able to use lo: interfaces for drbd.
+        * Make sure to use 0 as port number, so linux selects
+        *  a free one dynamically.
+        */
+        memcpy(&src_in6, mdev->net_conf->my_addr,
+               min_t(int, mdev->net_conf->my_addr_len, sizeof(src_in6)));
+        if (((struct sockaddr *)mdev->net_conf->my_addr)->sa_family == AF_INET6)
+                src_in6.sin6_port = 0;
+        else
+                ((struct sockaddr_in *)&src_in6)->sin_port = 0; /* AF_INET & AF_SCI */
+
+        what = "bind before connect";
+        err = sock->ops->bind(sock,
+                              (struct sockaddr *) &src_in6,
+                              mdev->net_conf->my_addr_len);
+        if (err < 0)
+                goto out;
+
+        /* connect may fail, peer not yet available.
+         * stay C_WF_CONNECTION, don't go Disconnecting! */
+        disconnect_on_error = 0;
+        what = "connect";
+        err = sock->ops->connect(sock,
+                                 (struct sockaddr *)mdev->net_conf->peer_addr,
+                                 mdev->net_conf->peer_addr_len, 0);
+
+out:
+        if (err < 0) {
+                if (sock) {
+                        sock_release(sock);
+                        sock = NULL;
+                }
+                switch (-err) {
+                        /* timeout, busy, signal pending */
+                case ETIMEDOUT: case EAGAIN: case EINPROGRESS:
+                case EINTR: case ERESTARTSYS:
+                        /* peer not (yet) available, network problem */
+                case ECONNREFUSED: case ENETUNREACH:
+                case EHOSTDOWN:    case EHOSTUNREACH:
+                        disconnect_on_error = 0;
+                        break;
+                default:
+                        dev_err(DEV, "%s failed, err = %d\n", what, err);
+                }
+                if (disconnect_on_error)
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+        }
+        put_net_conf(mdev);
+        return sock;
+}
+
+static struct socket *drbd_wait_for_connect(struct drbd_conf *mdev)
+{
+        int timeo, err;
+        struct socket *s_estab = NULL, *s_listen;
+        const char *what;
+
+        if (!get_net_conf(mdev))
+                return NULL;
+
+        what = "sock_create_kern";
+        err = sock_create_kern(((struct sockaddr *)mdev->net_conf->my_addr)->sa_family,
+                SOCK_STREAM, IPPROTO_TCP, &s_listen);
+        if (err) {
+                s_listen = NULL;
+                goto out;
+        }
+
+        timeo = mdev->net_conf->try_connect_int * HZ;
+        timeo += (random32() & 1) ? timeo / 7 : -timeo / 7; /* 28.5% random jitter */
+
+        s_listen->sk->sk_reuse    = 1; /* SO_REUSEADDR */
+        s_listen->sk->sk_rcvtimeo = timeo;
+        s_listen->sk->sk_sndtimeo = timeo;
+
+        what = "bind before listen";
+        err = s_listen->ops->bind(s_listen,
+                              (struct sockaddr *) mdev->net_conf->my_addr,
+                              mdev->net_conf->my_addr_len);
+        if (err < 0)
+                goto out;
+
+        err = drbd_accept(mdev, &what, s_listen, &s_estab);
+
+out:
+        if (s_listen)
+                sock_release(s_listen);
+        if (err < 0) {
+                if (err != -EAGAIN && err != -EINTR && err != -ERESTARTSYS) {
+                        dev_err(DEV, "%s failed, err = %d\n", what, err);
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                }
+        }
+        put_net_conf(mdev);
+
+        return s_estab;
+}
+
+static int drbd_send_fp(struct drbd_conf *mdev,
+        struct socket *sock, enum drbd_packets cmd)
+{
+        struct p_header *h = (struct p_header *) &mdev->data.sbuf.header;
+
+        return _drbd_send_cmd(mdev, sock, cmd, h, sizeof(*h), 0);
+}
+
+static enum drbd_packets drbd_recv_fp(struct drbd_conf *mdev, struct socket *sock)
+{
+        struct p_header *h = (struct p_header *) &mdev->data.sbuf.header;
+        int rr;
+
+        rr = drbd_recv_short(mdev, sock, h, sizeof(*h), 0);
+
+        if (rr == sizeof(*h) && h->magic == BE_DRBD_MAGIC)
+                return be16_to_cpu(h->command);
+
+        return 0xffff;
+}
+
+/**
+ * drbd_socket_okay() - Free the socket if its connection is not okay
+ * @mdev:       DRBD device.
+ * @sock:       pointer to the pointer to the socket.
+ */
+static int drbd_socket_okay(struct drbd_conf *mdev, struct socket **sock)
+{
+        int rr;
+        char tb[4];
+
+        if (!*sock)
+                return FALSE;
+
+        rr = drbd_recv_short(mdev, *sock, tb, 4, MSG_DONTWAIT | MSG_PEEK);
+
+        if (rr > 0 || rr == -EAGAIN) {
+                return TRUE;
+        } else {
+                sock_release(*sock);
+                *sock = NULL;
+                return FALSE;
+        }
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ *  -2 We do not have a network config...
+ */
+static int drbd_connect(struct drbd_conf *mdev)
+{
+        struct socket *s, *sock, *msock;
+        int try, h, ok;
+
+        D_ASSERT(!mdev->data.socket);
+
+        if (test_and_clear_bit(CREATE_BARRIER, &mdev->flags))
+                dev_err(DEV, "CREATE_BARRIER flag was set in drbd_connect - now cleared!\n");
+
+        if (drbd_request_state(mdev, NS(conn, C_WF_CONNECTION)) < SS_SUCCESS)
+                return -2;
+
+        clear_bit(DISCARD_CONCURRENT, &mdev->flags);
+
+        sock  = NULL;
+        msock = NULL;
+
+        do {
+                for (try = 0;;) {
+                        /* 3 tries, this should take less than a second! */
+                        s = drbd_try_connect(mdev);
+                        if (s || ++try >= 3)
+                                break;
+                        /* give the other side time to call bind() & listen() */
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(HZ / 10);
+                }
+
+                if (s) {
+                        if (!sock) {
+                                drbd_send_fp(mdev, s, P_HAND_SHAKE_S);
+                                sock = s;
+                                s = NULL;
+                        } else if (!msock) {
+                                drbd_send_fp(mdev, s, P_HAND_SHAKE_M);
+                                msock = s;
+                                s = NULL;
+                        } else {
+                                dev_err(DEV, "Logic error in drbd_connect()\n");
+                                goto out_release_sockets;
+                        }
+                }
+
+                if (sock && msock) {
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(HZ / 10);
+                        ok = drbd_socket_okay(mdev, &sock);
+                        ok = drbd_socket_okay(mdev, &msock) && ok;
+                        if (ok)
+                                break;
+                }
+
+retry:
+                s = drbd_wait_for_connect(mdev);
+                if (s) {
+                        try = drbd_recv_fp(mdev, s);
+                        drbd_socket_okay(mdev, &sock);
+                        drbd_socket_okay(mdev, &msock);
+                        switch (try) {
+                        case P_HAND_SHAKE_S:
+                                if (sock) {
+                                        dev_warn(DEV, "initial packet S crossed\n");
+                                        sock_release(sock);
+                                }
+                                sock = s;
+                                break;
+                        case P_HAND_SHAKE_M:
+                                if (msock) {
+                                        dev_warn(DEV, "initial packet M crossed\n");
+                                        sock_release(msock);
+                                }
+                                msock = s;
+                                set_bit(DISCARD_CONCURRENT, &mdev->flags);
+                                break;
+                        default:
+                                dev_warn(DEV, "Error receiving initial packet\n");
+                                sock_release(s);
+                                if (random32() & 1)
+                                        goto retry;
+                        }
+                }
+
+                if (mdev->state.conn <= C_DISCONNECTING)
+                        goto out_release_sockets;
+                if (signal_pending(current)) {
+                        flush_signals(current);
+                        smp_rmb();
+                        if (get_t_state(&mdev->receiver) == Exiting)
+                                goto out_release_sockets;
+                }
+
+                if (sock && msock) {
+                        ok = drbd_socket_okay(mdev, &sock);
+                        ok = drbd_socket_okay(mdev, &msock) && ok;
+                        if (ok)
+                                break;
+                }
+        } while (1);
+
+        msock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+        sock->sk->sk_reuse = 1; /* SO_REUSEADDR */
+
+        sock->sk->sk_allocation = GFP_NOIO;
+        msock->sk->sk_allocation = GFP_NOIO;
+
+        sock->sk->sk_priority = TC_PRIO_INTERACTIVE_BULK;
+        msock->sk->sk_priority = TC_PRIO_INTERACTIVE;
+
+        if (mdev->net_conf->sndbuf_size) {
+                sock->sk->sk_sndbuf = mdev->net_conf->sndbuf_size;
+                sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
+        }
+
+        if (mdev->net_conf->rcvbuf_size) {
+                sock->sk->sk_rcvbuf = mdev->net_conf->rcvbuf_size;
+                sock->sk->sk_userlocks |= SOCK_RCVBUF_LOCK;
+        }
+
+        /* NOT YET ...
+         * sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+         * sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+         * first set it to the P_HAND_SHAKE timeout,
+         * which we set to 4x the configured ping_timeout. */
+        sock->sk->sk_sndtimeo =
+        sock->sk->sk_rcvtimeo = mdev->net_conf->ping_timeo*4*HZ/10;
+
+        msock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+        msock->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+
+        /* we don't want delays.
+         * we use TCP_CORK where apropriate, though */
+        drbd_tcp_nodelay(sock);
+        drbd_tcp_nodelay(msock);
+
+        mdev->data.socket = sock;
+        mdev->meta.socket = msock;
+        mdev->last_received = jiffies;
+
+        D_ASSERT(mdev->asender.task == NULL);
+
+        h = drbd_do_handshake(mdev);
+        if (h <= 0)
+                return h;
+
+        if (mdev->cram_hmac_tfm) {
+                /* drbd_request_state(mdev, NS(conn, WFAuth)); */
+                if (!drbd_do_auth(mdev)) {
+                        dev_err(DEV, "Authentication of peer failed\n");
+                        return -1;
+                }
+        }
+
+        if (drbd_request_state(mdev, NS(conn, C_WF_REPORT_PARAMS)) < SS_SUCCESS)
+                return 0;
+
+        sock->sk->sk_sndtimeo = mdev->net_conf->timeout*HZ/10;
+        sock->sk->sk_rcvtimeo = MAX_SCHEDULE_TIMEOUT;
+
+        atomic_set(&mdev->packet_seq, 0);
+        mdev->peer_seq = 0;
+
+        drbd_thread_start(&mdev->asender);
+
+        drbd_send_protocol(mdev);
+        drbd_send_sync_param(mdev, &mdev->sync_conf);
+        drbd_send_sizes(mdev, 0);
+        drbd_send_uuids(mdev);
+        drbd_send_state(mdev);
+        clear_bit(USE_DEGR_WFC_T, &mdev->flags);
+        clear_bit(RESIZE_PENDING, &mdev->flags);
+
+        return 1;
+
+out_release_sockets:
+        if (sock)
+                sock_release(sock);
+        if (msock)
+                sock_release(msock);
+        return -1;
+}
+
+static int drbd_recv_header(struct drbd_conf *mdev, struct p_header *h)
+{
+        int r;
+
+        r = drbd_recv(mdev, h, sizeof(*h));
+
+        if (unlikely(r != sizeof(*h))) {
+                dev_err(DEV, "short read expecting header on sock: r=%d\n", r);
+                return FALSE;
+        };
+        h->command = be16_to_cpu(h->command);
+        h->length  = be16_to_cpu(h->length);
+        if (unlikely(h->magic != BE_DRBD_MAGIC)) {
+                dev_err(DEV, "magic?? on data m: 0x%lx c: %d l: %d\n",
+                    (long)be32_to_cpu(h->magic),
+                    h->command, h->length);
+                return FALSE;
+        }
+        mdev->last_received = jiffies;
+
+        return TRUE;
+}
+
+static enum finish_epoch drbd_flush_after_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch)
+{
+        int rv;
+
+        if (mdev->write_ordering >= WO_bdev_flush && get_ldev(mdev)) {
+                rv = blkdev_issue_flush(mdev->ldev->backing_bdev, NULL);
+                if (rv) {
+                        dev_err(DEV, "local disk flush failed with status %d\n", rv);
+                        /* would rather check on EOPNOTSUPP, but that is not reliable.
+                         * don't try again for ANY return value != 0
+                         * if (rv == -EOPNOTSUPP) */
+                        drbd_bump_write_ordering(mdev, WO_drain_io);
+                }
+                put_ldev(mdev);
+        }
+
+        return drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE);
+}
+
+static int w_flush(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct flush_work *fw = (struct flush_work *)w;
+        struct drbd_epoch *epoch = fw->epoch;
+
+        kfree(w);
+
+        if (!test_and_set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags))
+                drbd_flush_after_epoch(mdev, epoch);
+
+        drbd_may_finish_epoch(mdev, epoch, EV_PUT |
+                              (mdev->state.conn < C_CONNECTED ? EV_CLEANUP : 0));
+
+        return 1;
+}
+
+/**
+ * drbd_may_finish_epoch() - Applies an epoch_event to the epoch's state, eventually finishes it.
+ * @mdev:       DRBD device.
+ * @epoch:      Epoch object.
+ * @ev:         Epoch event.
+ */
+static enum finish_epoch drbd_may_finish_epoch(struct drbd_conf *mdev,
+                                               struct drbd_epoch *epoch,
+                                               enum epoch_event ev)
+{
+        int finish, epoch_size;
+        struct drbd_epoch *next_epoch;
+        int schedule_flush = 0;
+        enum finish_epoch rv = FE_STILL_LIVE;
+
+        spin_lock(&mdev->epoch_lock);
+        do {
+                next_epoch = NULL;
+                finish = 0;
+
+                epoch_size = atomic_read(&epoch->epoch_size);
+
+                switch (ev & ~EV_CLEANUP) {
+                case EV_PUT:
+                        atomic_dec(&epoch->active);
+                        break;
+                case EV_GOT_BARRIER_NR:
+                        set_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags);
+
+                        /* Special case: If we just switched from WO_bio_barrier to
+                           WO_bdev_flush we should not finish the current epoch */
+                        if (test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags) && epoch_size == 1 &&
+                            mdev->write_ordering != WO_bio_barrier &&
+                            epoch == mdev->current_epoch)
+                                clear_bit(DE_CONTAINS_A_BARRIER, &epoch->flags);
+                        break;
+                case EV_BARRIER_DONE:
+                        set_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags);
+                        break;
+                case EV_BECAME_LAST:
+                        /* nothing to do*/
+                        break;
+                }
+
+                trace_drbd_epoch(mdev, epoch, ev);
+
+                if (epoch_size != 0 &&
+                    atomic_read(&epoch->active) == 0 &&
+                    test_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags) &&
+                    epoch->list.prev == &mdev->current_epoch->list &&
+                    !test_bit(DE_IS_FINISHING, &epoch->flags)) {
+                        /* Nearly all conditions are met to finish that epoch... */
+                        if (test_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags) ||
+                            mdev->write_ordering == WO_none ||
+                            (epoch_size == 1 && test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags)) ||
+                            ev & EV_CLEANUP) {
+                                finish = 1;
+                                set_bit(DE_IS_FINISHING, &epoch->flags);
+                        } else if (!test_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags) &&
+                                 mdev->write_ordering == WO_bio_barrier) {
+                                atomic_inc(&epoch->active);
+                                schedule_flush = 1;
+                        }
+                }
+                if (finish) {
+                        if (!(ev & EV_CLEANUP)) {
+                                spin_unlock(&mdev->epoch_lock);
+                                drbd_send_b_ack(mdev, epoch->barrier_nr, epoch_size);
+                                spin_lock(&mdev->epoch_lock);
+                        }
+                        dec_unacked(mdev);
+
+                        if (mdev->current_epoch != epoch) {
+                                next_epoch = list_entry(epoch->list.next, struct drbd_epoch, list);
+                                list_del(&epoch->list);
+                                ev = EV_BECAME_LAST | (ev & EV_CLEANUP);
+                                mdev->epochs--;
+                                trace_drbd_epoch(mdev, epoch, EV_TRACE_FREE);
+                                kfree(epoch);
+
+                                if (rv == FE_STILL_LIVE)
+                                        rv = FE_DESTROYED;
+                        } else {
+                                epoch->flags = 0;
+                                atomic_set(&epoch->epoch_size, 0);
+                                /* atomic_set(&epoch->active, 0); is alrady zero */
+                                if (rv == FE_STILL_LIVE)
+                                        rv = FE_RECYCLED;
+                        }
+                }
+
+                if (!next_epoch)
+                        break;
+
+                epoch = next_epoch;
+        } while (1);
+
+        spin_unlock(&mdev->epoch_lock);
+
+        if (schedule_flush) {
+                struct flush_work *fw;
+                fw = kmalloc(sizeof(*fw), GFP_ATOMIC);
+                if (fw) {
+                        trace_drbd_epoch(mdev, epoch, EV_TRACE_FLUSH);
+                        fw->w.cb = w_flush;
+                        fw->epoch = epoch;
+                        drbd_queue_work(&mdev->data.work, &fw->w);
+                } else {
+                        dev_warn(DEV, "Could not kmalloc a flush_work obj\n");
+                        set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+                        /* That is not a recursion, only one level */
+                        drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE);
+                        drbd_may_finish_epoch(mdev, epoch, EV_PUT);
+                }
+        }
+
+        return rv;
+}
+
+/**
+ * drbd_bump_write_ordering() - Fall back to an other write ordering method
+ * @mdev:       DRBD device.
+ * @wo:         Write ordering method to try.
+ */
+void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo) __must_hold(local)
+{
+        enum write_ordering_e pwo;
+        static char *write_ordering_str[] = {
+                [WO_none] = "none",
+                [WO_drain_io] = "drain",
+                [WO_bdev_flush] = "flush",
+                [WO_bio_barrier] = "barrier",
+        };
+
+        pwo = mdev->write_ordering;
+        wo = min(pwo, wo);
+        if (wo == WO_bio_barrier && mdev->ldev->dc.no_disk_barrier)
+                wo = WO_bdev_flush;
+        if (wo == WO_bdev_flush && mdev->ldev->dc.no_disk_flush)
+                wo = WO_drain_io;
+        if (wo == WO_drain_io && mdev->ldev->dc.no_disk_drain)
+                wo = WO_none;
+        mdev->write_ordering = wo;
+        if (pwo != mdev->write_ordering || wo == WO_bio_barrier)
+                dev_info(DEV, "Method to ensure write ordering: %s\n", write_ordering_str[mdev->write_ordering]);
+}
+
+/**
+ * w_e_reissue() - Worker callback; Resubmit a bio, without BIO_RW_BARRIER set
+ * @mdev:       DRBD device.
+ * @w:          work object.
+ * @cancel:     The connection will be closed anyways (unused in this callback)
+ */
+int w_e_reissue(struct drbd_conf *mdev, struct drbd_work *w, int cancel) __releases(local)
+{
+        struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+        struct bio *bio = e->private_bio;
+
+        /* We leave DE_CONTAINS_A_BARRIER and EE_IS_BARRIER in place,
+           (and DE_BARRIER_IN_NEXT_EPOCH_ISSUED in the previous Epoch)
+           so that we can finish that epoch in drbd_may_finish_epoch().
+           That is necessary if we already have a long chain of Epochs, before
+           we realize that BIO_RW_BARRIER is actually not supported */
+
+        /* As long as the -ENOTSUPP on the barrier is reported immediately
+           that will never trigger. If it is reported late, we will just
+           print that warning and continue correctly for all future requests
+           with WO_bdev_flush */
+        if (previous_epoch(mdev, e->epoch))
+                dev_warn(DEV, "Write ordering was not enforced (one time event)\n");
+
+        /* prepare bio for re-submit,
+         * re-init volatile members */
+        /* we still have a local reference,
+         * get_ldev was done in receive_Data. */
+        bio->bi_bdev = mdev->ldev->backing_bdev;
+        bio->bi_sector = e->sector;
+        bio->bi_size = e->size;
+        bio->bi_idx = 0;
+
+        bio->bi_flags &= ~(BIO_POOL_MASK - 1);
+        bio->bi_flags |= 1 << BIO_UPTODATE;
+
+        /* don't know whether this is necessary: */
+        bio->bi_phys_segments = 0;
+        bio->bi_next = NULL;
+
+        /* these should be unchanged: */
+        /* bio->bi_end_io = drbd_endio_write_sec; */
+        /* bio->bi_vcnt = whatever; */
+
+        e->w.cb = e_end_block;
+
+        /* This is no longer a barrier request. */
+        bio->bi_rw &= ~(1UL << BIO_RW_BARRIER);
+
+        drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, bio);
+
+        return 1;
+}
+
+static int receive_Barrier(struct drbd_conf *mdev, struct p_header *h)
+{
+        int rv, issue_flush;
+        struct p_barrier *p = (struct p_barrier *)h;
+        struct drbd_epoch *epoch;
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+
+        rv = drbd_recv(mdev, h->payload, h->length);
+        ERR_IF(rv != h->length) return FALSE;
+
+        inc_unacked(mdev);
+
+        if (mdev->net_conf->wire_protocol != DRBD_PROT_C)
+                drbd_kick_lo(mdev);
+
+        mdev->current_epoch->barrier_nr = p->barrier;
+        rv = drbd_may_finish_epoch(mdev, mdev->current_epoch, EV_GOT_BARRIER_NR);
+
+        /* P_BARRIER_ACK may imply that the corresponding extent is dropped from
+         * the activity log, which means it would not be resynced in case the
+         * R_PRIMARY crashes now.
+         * Therefore we must send the barrier_ack after the barrier request was
+         * completed. */
+        switch (mdev->write_ordering) {
+        case WO_bio_barrier:
+        case WO_none:
+                if (rv == FE_RECYCLED)
+                        return TRUE;
+                break;
+
+        case WO_bdev_flush:
+        case WO_drain_io:
+                D_ASSERT(rv == FE_STILL_LIVE);
+                set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &mdev->current_epoch->flags);
+                drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+                rv = drbd_flush_after_epoch(mdev, mdev->current_epoch);
+                if (rv == FE_RECYCLED)
+                        return TRUE;
+
+                /* The asender will send all the ACKs and barrier ACKs out, since
+                   all EEs moved from the active_ee to the done_ee. We need to
+                   provide a new epoch object for the EEs that come in soon */
+                break;
+        }
+
+        /* receiver context, in the writeout path of the other node.
+         * avoid potential distributed deadlock */
+        epoch = kmalloc(sizeof(struct drbd_epoch), GFP_NOIO);
+        if (!epoch) {
+                dev_warn(DEV, "Allocation of an epoch failed, slowing down\n");
+                issue_flush = !test_and_set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+                drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+                if (issue_flush) {
+                        rv = drbd_flush_after_epoch(mdev, mdev->current_epoch);
+                        if (rv == FE_RECYCLED)
+                                return TRUE;
+                }
+
+                drbd_wait_ee_list_empty(mdev, &mdev->done_ee);
+
+                return TRUE;
+        }
+
+        epoch->flags = 0;
+        atomic_set(&epoch->epoch_size, 0);
+        atomic_set(&epoch->active, 0);
+
+        spin_lock(&mdev->epoch_lock);
+        if (atomic_read(&mdev->current_epoch->epoch_size)) {
+                list_add(&epoch->list, &mdev->current_epoch->list);
+                mdev->current_epoch = epoch;
+                mdev->epochs++;
+                trace_drbd_epoch(mdev, epoch, EV_TRACE_ALLOC);
+        } else {
+                /* The current_epoch got recycled while we allocated this one... */
+                kfree(epoch);
+        }
+        spin_unlock(&mdev->epoch_lock);
+
+        return TRUE;
+}
+
+/* used from receive_RSDataReply (recv_resync_read)
+ * and from receive_Data */
+static struct drbd_epoch_entry *
+read_in_block(struct drbd_conf *mdev, u64 id, sector_t sector, int data_size) __must_hold(local)
+{
+        struct drbd_epoch_entry *e;
+        struct bio_vec *bvec;
+        struct page *page;
+        struct bio *bio;
+        int dgs, ds, i, rr;
+        void *dig_in = mdev->int_dig_in;
+        void *dig_vv = mdev->int_dig_vv;
+
+        dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+                crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+        if (dgs) {
+                rr = drbd_recv(mdev, dig_in, dgs);
+                if (rr != dgs) {
+                        dev_warn(DEV, "short read receiving data digest: read %d expected %d\n",
+                             rr, dgs);
+                        return NULL;
+                }
+        }
+
+        data_size -= dgs;
+
+        ERR_IF(data_size &  0x1ff) return NULL;
+        ERR_IF(data_size >  DRBD_MAX_SEGMENT_SIZE) return NULL;
+
+        /* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+         * "criss-cross" setup, that might cause write-out on some other DRBD,
+         * which in turn might block on the other node at this very place.  */
+        e = drbd_alloc_ee(mdev, id, sector, data_size, GFP_NOIO);
+        if (!e)
+                return NULL;
+        bio = e->private_bio;
+        ds = data_size;
+        bio_for_each_segment(bvec, bio, i) {
+                page = bvec->bv_page;
+                rr = drbd_recv(mdev, kmap(page), min_t(int, ds, PAGE_SIZE));
+                kunmap(page);
+                if (rr != min_t(int, ds, PAGE_SIZE)) {
+                        drbd_free_ee(mdev, e);
+                        dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+                             rr, min_t(int, ds, PAGE_SIZE));
+                        return NULL;
+                }
+                ds -= rr;
+        }
+
+        if (dgs) {
+                drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+                if (memcmp(dig_in, dig_vv, dgs)) {
+                        dev_err(DEV, "Digest integrity check FAILED.\n");
+                        drbd_bcast_ee(mdev, "digest failed",
+                                        dgs, dig_in, dig_vv, e);
+                        drbd_free_ee(mdev, e);
+                        return NULL;
+                }
+        }
+        mdev->recv_cnt += data_size>>9;
+        return e;
+}
+
+/* drbd_drain_block() just takes a data block
+ * out of the socket input buffer, and discards it.
+ */
+static int drbd_drain_block(struct drbd_conf *mdev, int data_size)
+{
+        struct page *page;
+        int rr, rv = 1;
+        void *data;
+
+        page = drbd_pp_alloc(mdev, 1);
+
+        data = kmap(page);
+        while (data_size) {
+                rr = drbd_recv(mdev, data, min_t(int, data_size, PAGE_SIZE));
+                if (rr != min_t(int, data_size, PAGE_SIZE)) {
+                        rv = 0;
+                        dev_warn(DEV, "short read receiving data: read %d expected %d\n",
+                             rr, min_t(int, data_size, PAGE_SIZE));
+                        break;
+                }
+                data_size -= rr;
+        }
+        kunmap(page);
+        drbd_pp_free(mdev, page);
+        return rv;
+}
+
+static int recv_dless_read(struct drbd_conf *mdev, struct drbd_request *req,
+                           sector_t sector, int data_size)
+{
+        struct bio_vec *bvec;
+        struct bio *bio;
+        int dgs, rr, i, expect;
+        void *dig_in = mdev->int_dig_in;
+        void *dig_vv = mdev->int_dig_vv;
+
+        dgs = (mdev->agreed_pro_version >= 87 && mdev->integrity_r_tfm) ?
+                crypto_hash_digestsize(mdev->integrity_r_tfm) : 0;
+
+        if (dgs) {
+                rr = drbd_recv(mdev, dig_in, dgs);
+                if (rr != dgs) {
+                        dev_warn(DEV, "short read receiving data reply digest: read %d expected %d\n",
+                             rr, dgs);
+                        return 0;
+                }
+        }
+
+        data_size -= dgs;
+
+        /* optimistically update recv_cnt.  if receiving fails below,
+         * we disconnect anyways, and counters will be reset. */
+        mdev->recv_cnt += data_size>>9;
+
+        bio = req->master_bio;
+        D_ASSERT(sector == bio->bi_sector);
+
+        bio_for_each_segment(bvec, bio, i) {
+                expect = min_t(int, data_size, bvec->bv_len);
+                rr = drbd_recv(mdev,
+                             kmap(bvec->bv_page)+bvec->bv_offset,
+                             expect);
+                kunmap(bvec->bv_page);
+                if (rr != expect) {
+                        dev_warn(DEV, "short read receiving data reply: "
+                             "read %d expected %d\n",
+                             rr, expect);
+                        return 0;
+                }
+                data_size -= rr;
+        }
+
+        if (dgs) {
+                drbd_csum(mdev, mdev->integrity_r_tfm, bio, dig_vv);
+                if (memcmp(dig_in, dig_vv, dgs)) {
+                        dev_err(DEV, "Digest integrity check FAILED. Broken NICs?\n");
+                        return 0;
+                }
+        }
+
+        D_ASSERT(data_size == 0);
+        return 1;
+}
+
+/* e_end_resync_block() is called via
+ * drbd_process_done_ee() by asender only */
+static int e_end_resync_block(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+        sector_t sector = e->sector;
+        int ok;
+
+        D_ASSERT(hlist_unhashed(&e->colision));
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                drbd_set_in_sync(mdev, sector, e->size);
+                ok = drbd_send_ack(mdev, P_RS_WRITE_ACK, e);
+        } else {
+                /* Record failure to sync */
+                drbd_rs_failed_io(mdev, sector, e->size);
+
+                ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+        }
+        dec_unacked(mdev);
+
+        return ok;
+}
+
+static int recv_resync_read(struct drbd_conf *mdev, sector_t sector, int data_size) __releases(local)
+{
+        struct drbd_epoch_entry *e;
+
+        e = read_in_block(mdev, ID_SYNCER, sector, data_size);
+        if (!e) {
+                put_ldev(mdev);
+                return FALSE;
+        }
+
+        dec_rs_pending(mdev);
+
+        e->private_bio->bi_end_io = drbd_endio_write_sec;
+        e->private_bio->bi_rw = WRITE;
+        e->w.cb = e_end_resync_block;
+
+        inc_unacked(mdev);
+        /* corresponding dec_unacked() in e_end_resync_block()
+         * respective _drbd_clear_done_ee */
+
+        spin_lock_irq(&mdev->req_lock);
+        list_add(&e->w.list, &mdev->sync_ee);
+        spin_unlock_irq(&mdev->req_lock);
+
+        trace_drbd_ee(mdev, e, "submitting for (rs)write");
+        trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+        drbd_generic_make_request(mdev, DRBD_FAULT_RS_WR, e->private_bio);
+        /* accounting done in endio */
+
+        maybe_kick_lo(mdev);
+        return TRUE;
+}
+
+static int receive_DataReply(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct drbd_request *req;
+        sector_t sector;
+        unsigned int header_size, data_size;
+        int ok;
+        struct p_data *p = (struct p_data *)h;
+
+        header_size = sizeof(*p) - sizeof(*h);
+        data_size   = h->length  - header_size;
+
+        ERR_IF(data_size == 0) return FALSE;
+
+        if (drbd_recv(mdev, h->payload, header_size) != header_size)
+                return FALSE;
+
+        sector = be64_to_cpu(p->sector);
+
+        spin_lock_irq(&mdev->req_lock);
+        req = _ar_id_to_req(mdev, p->block_id, sector);
+        spin_unlock_irq(&mdev->req_lock);
+        if (unlikely(!req)) {
+                dev_err(DEV, "Got a corrupt block_id/sector pair(1).\n");
+                return FALSE;
+        }
+
+        /* hlist_del(&req->colision) is done in _req_may_be_done, to avoid
+         * special casing it there for the various failure cases.
+         * still no race with drbd_fail_pending_reads */
+        ok = recv_dless_read(mdev, req, sector, data_size);
+
+        if (ok)
+                req_mod(req, data_received);
+        /* else: nothing. handled from drbd_disconnect...
+         * I don't think we may complete this just yet
+         * in case we are "on-disconnect: freeze" */
+
+        return ok;
+}
+
+static int receive_RSDataReply(struct drbd_conf *mdev, struct p_header *h)
+{
+        sector_t sector;
+        unsigned int header_size, data_size;
+        int ok;
+        struct p_data *p = (struct p_data *)h;
+
+        header_size = sizeof(*p) - sizeof(*h);
+        data_size   = h->length  - header_size;
+
+        ERR_IF(data_size == 0) return FALSE;
+
+        if (drbd_recv(mdev, h->payload, header_size) != header_size)
+                return FALSE;
+
+        sector = be64_to_cpu(p->sector);
+        D_ASSERT(p->block_id == ID_SYNCER);
+
+        if (get_ldev(mdev)) {
+                /* data is submitted to disk within recv_resync_read.
+                 * corresponding put_ldev done below on error,
+                 * or in drbd_endio_write_sec. */
+                ok = recv_resync_read(mdev, sector, data_size);
+        } else {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Can not write resync data to local disk.\n");
+
+                ok = drbd_drain_block(mdev, data_size);
+
+                drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+        }
+
+        return ok;
+}
+
+/* e_end_block() is called via drbd_process_done_ee().
+ * this means this function only runs in the asender thread
+ */
+static int e_end_block(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+        sector_t sector = e->sector;
+        struct drbd_epoch *epoch;
+        int ok = 1, pcmd;
+
+        if (e->flags & EE_IS_BARRIER) {
+                epoch = previous_epoch(mdev, e->epoch);
+                if (epoch)
+                        drbd_may_finish_epoch(mdev, epoch, EV_BARRIER_DONE + (cancel ? EV_CLEANUP : 0));
+        }
+
+        if (mdev->net_conf->wire_protocol == DRBD_PROT_C) {
+                if (likely(drbd_bio_uptodate(e->private_bio))) {
+                        pcmd = (mdev->state.conn >= C_SYNC_SOURCE &&
+                                mdev->state.conn <= C_PAUSED_SYNC_T &&
+                                e->flags & EE_MAY_SET_IN_SYNC) ?
+                                P_RS_WRITE_ACK : P_WRITE_ACK;
+                        ok &= drbd_send_ack(mdev, pcmd, e);
+                        if (pcmd == P_RS_WRITE_ACK)
+                                drbd_set_in_sync(mdev, sector, e->size);
+                } else {
+                        ok  = drbd_send_ack(mdev, P_NEG_ACK, e);
+                        /* we expect it to be marked out of sync anyways...
+                         * maybe assert this?  */
+                }
+                dec_unacked(mdev);
+        }
+        /* we delete from the conflict detection hash _after_ we sent out the
+         * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
+        if (mdev->net_conf->two_primaries) {
+                spin_lock_irq(&mdev->req_lock);
+                D_ASSERT(!hlist_unhashed(&e->colision));
+                hlist_del_init(&e->colision);
+                spin_unlock_irq(&mdev->req_lock);
+        } else {
+                D_ASSERT(hlist_unhashed(&e->colision));
+        }
+
+        drbd_may_finish_epoch(mdev, e->epoch, EV_PUT + (cancel ? EV_CLEANUP : 0));
+
+        return ok;
+}
+
+static int e_send_discard_ack(struct drbd_conf *mdev, struct drbd_work *w, int unused)
+{
+        struct drbd_epoch_entry *e = (struct drbd_epoch_entry *)w;
+        int ok = 1;
+
+        D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+        ok = drbd_send_ack(mdev, P_DISCARD_ACK, e);
+
+        spin_lock_irq(&mdev->req_lock);
+        D_ASSERT(!hlist_unhashed(&e->colision));
+        hlist_del_init(&e->colision);
+        spin_unlock_irq(&mdev->req_lock);
+
+        dec_unacked(mdev);
+
+        return ok;
+}
+
+/* Called from receive_Data.
+ * Synchronize packets on sock with packets on msock.
+ *
+ * This is here so even when a P_DATA packet traveling via sock overtook an Ack
+ * packet traveling on msock, they are still processed in the order they have
+ * been sent.
+ *
+ * Note: we don't care for Ack packets overtaking P_DATA packets.
+ *
+ * In case packet_seq is larger than mdev->peer_seq number, there are
+ * outstanding packets on the msock. We wait for them to arrive.
+ * In case we are the logically next packet, we update mdev->peer_seq
+ * ourselves. Correctly handles 32bit wrap around.
+ *
+ * Assume we have a 10 GBit connection, that is about 1<<30 byte per second,
+ * about 1<<21 sectors per second. So "worst" case, we have 1<<3 == 8 seconds
+ * for the 24bit wrap (historical atomic_t guarantee on some archs), and we have
+ * 1<<9 == 512 seconds aka ages for the 32bit wrap around...
+ *
+ * returns 0 if we may process the packet,
+ * -ERESTARTSYS if we were interrupted (by disconnect signal). */
+static int drbd_wait_peer_seq(struct drbd_conf *mdev, const u32 packet_seq)
+{
+        DEFINE_WAIT(wait);
+        unsigned int p_seq;
+        long timeout;
+        int ret = 0;
+        spin_lock(&mdev->peer_seq_lock);
+        for (;;) {
+                prepare_to_wait(&mdev->seq_wait, &wait, TASK_INTERRUPTIBLE);
+                if (seq_le(packet_seq, mdev->peer_seq+1))
+                        break;
+                if (signal_pending(current)) {
+                        ret = -ERESTARTSYS;
+                        break;
+                }
+                p_seq = mdev->peer_seq;
+                spin_unlock(&mdev->peer_seq_lock);
+                timeout = schedule_timeout(30*HZ);
+                spin_lock(&mdev->peer_seq_lock);
+                if (timeout == 0 && p_seq == mdev->peer_seq) {
+                        ret = -ETIMEDOUT;
+                        dev_err(DEV, "ASSERT FAILED waited 30 seconds for sequence update, forcing reconnect\n");
+                        break;
+                }
+        }
+        finish_wait(&mdev->seq_wait, &wait);
+        if (mdev->peer_seq+1 == packet_seq)
+                mdev->peer_seq++;
+        spin_unlock(&mdev->peer_seq_lock);
+        return ret;
+}
+
+/* mirrored write */
+static int receive_Data(struct drbd_conf *mdev, struct p_header *h)
+{
+        sector_t sector;
+        struct drbd_epoch_entry *e;
+        struct p_data *p = (struct p_data *)h;
+        int header_size, data_size;
+        int rw = WRITE;
+        u32 dp_flags;
+
+        header_size = sizeof(*p) - sizeof(*h);
+        data_size   = h->length  - header_size;
+
+        ERR_IF(data_size == 0) return FALSE;
+
+        if (drbd_recv(mdev, h->payload, header_size) != header_size)
+                return FALSE;
+
+        if (!get_ldev(mdev)) {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Can not write mirrored data block "
+                            "to local disk.\n");
+                spin_lock(&mdev->peer_seq_lock);
+                if (mdev->peer_seq+1 == be32_to_cpu(p->seq_num))
+                        mdev->peer_seq++;
+                spin_unlock(&mdev->peer_seq_lock);
+
+                drbd_send_ack_dp(mdev, P_NEG_ACK, p);
+                atomic_inc(&mdev->current_epoch->epoch_size);
+                return drbd_drain_block(mdev, data_size);
+        }
+
+        /* get_ldev(mdev) successful.
+         * Corresponding put_ldev done either below (on various errors),
+         * or in drbd_endio_write_sec, if we successfully submit the data at
+         * the end of this function. */
+
+        sector = be64_to_cpu(p->sector);
+        e = read_in_block(mdev, p->block_id, sector, data_size);
+        if (!e) {
+                put_ldev(mdev);
+                return FALSE;
+        }
+
+        e->private_bio->bi_end_io = drbd_endio_write_sec;
+        e->w.cb = e_end_block;
+
+        spin_lock(&mdev->epoch_lock);
+        e->epoch = mdev->current_epoch;
+        atomic_inc(&e->epoch->epoch_size);
+        atomic_inc(&e->epoch->active);
+
+        if (mdev->write_ordering == WO_bio_barrier && atomic_read(&e->epoch->epoch_size) == 1) {
+                struct drbd_epoch *epoch;
+                /* Issue a barrier if we start a new epoch, and the previous epoch
+                   was not a epoch containing a single request which already was
+                   a Barrier. */
+                epoch = list_entry(e->epoch->list.prev, struct drbd_epoch, list);
+                if (epoch == e->epoch) {
+                        set_bit(DE_CONTAINS_A_BARRIER, &e->epoch->flags);
+                        trace_drbd_epoch(mdev, e->epoch, EV_TRACE_ADD_BARRIER);
+                        rw |= (1<<BIO_RW_BARRIER);
+                        e->flags |= EE_IS_BARRIER;
+                } else {
+                        if (atomic_read(&epoch->epoch_size) > 1 ||
+                            !test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags)) {
+                                set_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags);
+                                trace_drbd_epoch(mdev, epoch, EV_TRACE_SETTING_BI);
+                                set_bit(DE_CONTAINS_A_BARRIER, &e->epoch->flags);
+                                trace_drbd_epoch(mdev, e->epoch, EV_TRACE_ADD_BARRIER);
+                                rw |= (1<<BIO_RW_BARRIER);
+                                e->flags |= EE_IS_BARRIER;
+                        }
+                }
+        }
+        spin_unlock(&mdev->epoch_lock);
+
+        dp_flags = be32_to_cpu(p->dp_flags);
+        if (dp_flags & DP_HARDBARRIER) {
+                dev_err(DEV, "ASSERT FAILED would have submitted barrier request\n");
+                /* rw |= (1<<BIO_RW_BARRIER); */
+        }
+        if (dp_flags & DP_RW_SYNC)
+                rw |= (1<<BIO_RW_SYNCIO) | (1<<BIO_RW_UNPLUG);
+        if (dp_flags & DP_MAY_SET_IN_SYNC)
+                e->flags |= EE_MAY_SET_IN_SYNC;
+
+        /* I'm the receiver, I do hold a net_cnt reference. */
+        if (!mdev->net_conf->two_primaries) {
+                spin_lock_irq(&mdev->req_lock);
+        } else {
+                /* don't get the req_lock yet,
+                 * we may sleep in drbd_wait_peer_seq */
+                const int size = e->size;
+                const int discard = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+                DEFINE_WAIT(wait);
+                struct drbd_request *i;
+                struct hlist_node *n;
+                struct hlist_head *slot;
+                int first;
+
+                D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+                BUG_ON(mdev->ee_hash == NULL);
+                BUG_ON(mdev->tl_hash == NULL);
+
+                /* conflict detection and handling:
+                 * 1. wait on the sequence number,
+                 *    in case this data packet overtook ACK packets.
+                 * 2. check our hash tables for conflicting requests.
+                 *    we only need to walk the tl_hash, since an ee can not
+                 *    have a conflict with an other ee: on the submitting
+                 *    node, the corresponding req had already been conflicting,
+                 *    and a conflicting req is never sent.
+                 *
+                 * Note: for two_primaries, we are protocol C,
+                 * so there cannot be any request that is DONE
+                 * but still on the transfer log.
+                 *
+                 * unconditionally add to the ee_hash.
+                 *
+                 * if no conflicting request is found:
+                 *    submit.
+                 *
+                 * if any conflicting request is found
+                 * that has not yet been acked,
+                 * AND I have the "discard concurrent writes" flag:
+                 *       queue (via done_ee) the P_DISCARD_ACK; OUT.
+                 *
+                 * if any conflicting request is found:
+                 *       block the receiver, waiting on misc_wait
+                 *       until no more conflicting requests are there,
+                 *       or we get interrupted (disconnect).
+                 *
+                 *       we do not just write after local io completion of those
+                 *       requests, but only after req is done completely, i.e.
+                 *       we wait for the P_DISCARD_ACK to arrive!
+                 *
+                 *       then proceed normally, i.e. submit.
+                 */
+                if (drbd_wait_peer_seq(mdev, be32_to_cpu(p->seq_num)))
+                        goto out_interrupted;
+
+                spin_lock_irq(&mdev->req_lock);
+
+                hlist_add_head(&e->colision, ee_hash_slot(mdev, sector));
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+                slot = tl_hash_slot(mdev, sector);
+                first = 1;
+                for (;;) {
+                        int have_unacked = 0;
+                        int have_conflict = 0;
+                        prepare_to_wait(&mdev->misc_wait, &wait,
+                                TASK_INTERRUPTIBLE);
+                        hlist_for_each_entry(i, n, slot, colision) {
+                                if (OVERLAPS) {
+                                        /* only ALERT on first iteration,
+                                         * we may be woken up early... */
+                                        if (first)
+                                                dev_alert(DEV, "%s[%u] Concurrent local write detected!"
+                                                      " new: %llus +%u; pending: %llus +%u\n",
+                                                      current->comm, current->pid,
+                                                      (unsigned long long)sector, size,
+                                                      (unsigned long long)i->sector, i->size);
+                                        if (i->rq_state & RQ_NET_PENDING)
+                                                ++have_unacked;
+                                        ++have_conflict;
+                                }
+                        }
+#undef OVERLAPS
+                        if (!have_conflict)
+                                break;
+
+                        /* Discard Ack only for the _first_ iteration */
+                        if (first && discard && have_unacked) {
+                                dev_alert(DEV, "Concurrent write! [DISCARD BY FLAG] sec=%llus\n",
+                                     (unsigned long long)sector);
+                                inc_unacked(mdev);
+                                e->w.cb = e_send_discard_ack;
+                                list_add_tail(&e->w.list, &mdev->done_ee);
+
+                                spin_unlock_irq(&mdev->req_lock);
+
+                                /* we could probably send that P_DISCARD_ACK ourselves,
+                                 * but I don't like the receiver using the msock */
+
+                                put_ldev(mdev);
+                                wake_asender(mdev);
+                                finish_wait(&mdev->misc_wait, &wait);
+                                return TRUE;
+                        }
+
+                        if (signal_pending(current)) {
+                                hlist_del_init(&e->colision);
+
+                                spin_unlock_irq(&mdev->req_lock);
+
+                                finish_wait(&mdev->misc_wait, &wait);
+                                goto out_interrupted;
+                        }
+
+                        spin_unlock_irq(&mdev->req_lock);
+                        if (first) {
+                                first = 0;
+                                dev_alert(DEV, "Concurrent write! [W AFTERWARDS] "
+                                     "sec=%llus\n", (unsigned long long)sector);
+                        } else if (discard) {
+                                /* we had none on the first iteration.
+                                 * there must be none now. */
+                                D_ASSERT(have_unacked == 0);
+                        }
+                        schedule();
+                        spin_lock_irq(&mdev->req_lock);
+                }
+                finish_wait(&mdev->misc_wait, &wait);
+        }
+
+        list_add(&e->w.list, &mdev->active_ee);
+        spin_unlock_irq(&mdev->req_lock);
+
+        switch (mdev->net_conf->wire_protocol) {
+        case DRBD_PROT_C:
+                inc_unacked(mdev);
+                /* corresponding dec_unacked() in e_end_block()
+                 * respective _drbd_clear_done_ee */
+                break;
+        case DRBD_PROT_B:
+                /* I really don't like it that the receiver thread
+                 * sends on the msock, but anyways */
+                drbd_send_ack(mdev, P_RECV_ACK, e);
+                break;
+        case DRBD_PROT_A:
+                /* nothing to do */
+                break;
+        }
+
+        if (mdev->state.pdsk == D_DISKLESS) {
+                /* In case we have the only disk of the cluster, */
+                drbd_set_out_of_sync(mdev, e->sector, e->size);
+                e->flags |= EE_CALL_AL_COMPLETE_IO;
+                drbd_al_begin_io(mdev, e->sector);
+        }
+
+        e->private_bio->bi_rw = rw;
+        trace_drbd_ee(mdev, e, "submitting for (data)write");
+        trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+        drbd_generic_make_request(mdev, DRBD_FAULT_DT_WR, e->private_bio);
+        /* accounting done in endio */
+
+        maybe_kick_lo(mdev);
+        return TRUE;
+
+out_interrupted:
+        /* yes, the epoch_size now is imbalanced.
+         * but we drop the connection anyways, so we don't have a chance to
+         * receive a barrier... atomic_inc(&mdev->epoch_size); */
+        put_ldev(mdev);
+        drbd_free_ee(mdev, e);
+        return FALSE;
+}
+
+static int receive_DataRequest(struct drbd_conf *mdev, struct p_header *h)
+{
+        sector_t sector;
+        const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+        struct drbd_epoch_entry *e;
+        struct digest_info *di = NULL;
+        int size, digest_size;
+        unsigned int fault_type;
+        struct p_block_req *p =
+                (struct p_block_req *)h;
+        const int brps = sizeof(*p)-sizeof(*h);
+
+        if (drbd_recv(mdev, h->payload, brps) != brps)
+                return FALSE;
+
+        sector = be64_to_cpu(p->sector);
+        size   = be32_to_cpu(p->blksize);
+
+        if (size <= 0 || (size & 0x1ff) != 0 || size > DRBD_MAX_SEGMENT_SIZE) {
+                dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+                                (unsigned long long)sector, size);
+                return FALSE;
+        }
+        if (sector + (size>>9) > capacity) {
+                dev_err(DEV, "%s:%d: sector: %llus, size: %u\n", __FILE__, __LINE__,
+                                (unsigned long long)sector, size);
+                return FALSE;
+        }
+
+        if (!get_ldev_if_state(mdev, D_UP_TO_DATE)) {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Can not satisfy peer's read request, "
+                            "no local data.\n");
+                drbd_send_ack_rp(mdev, h->command == P_DATA_REQUEST ? P_NEG_DREPLY :
+                                 P_NEG_RS_DREPLY , p);
+                return TRUE;
+        }
+
+        /* GFP_NOIO, because we must not cause arbitrary write-out: in a DRBD
+         * "criss-cross" setup, that might cause write-out on some other DRBD,
+         * which in turn might block on the other node at this very place.  */
+        e = drbd_alloc_ee(mdev, p->block_id, sector, size, GFP_NOIO);
+        if (!e) {
+                put_ldev(mdev);
+                return FALSE;
+        }
+
+        e->private_bio->bi_rw = READ;
+        e->private_bio->bi_end_io = drbd_endio_read_sec;
+
+        switch (h->command) {
+        case P_DATA_REQUEST:
+                e->w.cb = w_e_end_data_req;
+                fault_type = DRBD_FAULT_DT_RD;
+                break;
+        case P_RS_DATA_REQUEST:
+                e->w.cb = w_e_end_rsdata_req;
+                fault_type = DRBD_FAULT_RS_RD;
+                /* Eventually this should become asynchronously. Currently it
+                 * blocks the whole receiver just to delay the reading of a
+                 * resync data block.
+                 * the drbd_work_queue mechanism is made for this...
+                 */
+                if (!drbd_rs_begin_io(mdev, sector)) {
+                        /* we have been interrupted,
+                         * probably connection lost! */
+                        D_ASSERT(signal_pending(current));
+                        goto out_free_e;
+                }
+                break;
+
+        case P_OV_REPLY:
+        case P_CSUM_RS_REQUEST:
+                fault_type = DRBD_FAULT_RS_RD;
+                digest_size = h->length - brps ;
+                di = kmalloc(sizeof(*di) + digest_size, GFP_NOIO);
+                if (!di)
+                        goto out_free_e;
+
+                di->digest_size = digest_size;
+                di->digest = (((char *)di)+sizeof(struct digest_info));
+
+                if (drbd_recv(mdev, di->digest, digest_size) != digest_size)
+                        goto out_free_e;
+
+                e->block_id = (u64)(unsigned long)di;
+                if (h->command == P_CSUM_RS_REQUEST) {
+                        D_ASSERT(mdev->agreed_pro_version >= 89);
+                        e->w.cb = w_e_end_csum_rs_req;
+                } else if (h->command == P_OV_REPLY) {
+                        e->w.cb = w_e_end_ov_reply;
+                        dec_rs_pending(mdev);
+                        break;
+                }
+
+                if (!drbd_rs_begin_io(mdev, sector)) {
+                        /* we have been interrupted, probably connection lost! */
+                        D_ASSERT(signal_pending(current));
+                        goto out_free_e;
+                }
+                break;
+
+        case P_OV_REQUEST:
+                if (mdev->state.conn >= C_CONNECTED &&
+                    mdev->state.conn != C_VERIFY_T)
+                        dev_warn(DEV, "ASSERT FAILED: got P_OV_REQUEST while being %s\n",
+                                drbd_conn_str(mdev->state.conn));
+                if (mdev->ov_start_sector == ~(sector_t)0 &&
+                    mdev->agreed_pro_version >= 90) {
+                        mdev->ov_start_sector = sector;
+                        mdev->ov_position = sector;
+                        mdev->ov_left = mdev->rs_total - BM_SECT_TO_BIT(sector);
+                        dev_info(DEV, "Online Verify start sector: %llu\n",
+                                        (unsigned long long)sector);
+                }
+                e->w.cb = w_e_end_ov_req;
+                fault_type = DRBD_FAULT_RS_RD;
+                /* Eventually this should become asynchronous. Currently it
+                 * blocks the whole receiver just to delay the reading of a
+                 * resync data block.
+                 * the drbd_work_queue mechanism is made for this...
+                 */
+                if (!drbd_rs_begin_io(mdev, sector)) {
+                        /* we have been interrupted,
+                         * probably connection lost! */
+                        D_ASSERT(signal_pending(current));
+                        goto out_free_e;
+                }
+                break;
+
+
+        default:
+                dev_err(DEV, "unexpected command (%s) in receive_DataRequest\n",
+                    cmdname(h->command));
+                fault_type = DRBD_FAULT_MAX;
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        list_add(&e->w.list, &mdev->read_ee);
+        spin_unlock_irq(&mdev->req_lock);
+
+        inc_unacked(mdev);
+
+        trace_drbd_ee(mdev, e, "submitting for read");
+        trace_drbd_bio(mdev, "Sec", e->private_bio, 0, NULL);
+        drbd_generic_make_request(mdev, fault_type, e->private_bio);
+        maybe_kick_lo(mdev);
+
+        return TRUE;
+
+out_free_e:
+        kfree(di);
+        put_ldev(mdev);
+        drbd_free_ee(mdev, e);
+        return FALSE;
+}
+
+static int drbd_asb_recover_0p(struct drbd_conf *mdev) __must_hold(local)
+{
+        int self, peer, rv = -100;
+        unsigned long ch_self, ch_peer;
+
+        self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+        peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+        ch_peer = mdev->p_uuid[UI_SIZE];
+        ch_self = mdev->comm_bm_set;
+
+        switch (mdev->net_conf->after_sb_0p) {
+        case ASB_CONSENSUS:
+        case ASB_DISCARD_SECONDARY:
+        case ASB_CALL_HELPER:
+                dev_err(DEV, "Configuration error.\n");
+                break;
+        case ASB_DISCONNECT:
+                break;
+        case ASB_DISCARD_YOUNGER_PRI:
+                if (self == 0 && peer == 1) {
+                        rv = -1;
+                        break;
+                }
+                if (self == 1 && peer == 0) {
+                        rv =  1;
+                        break;
+                }
+                /* Else fall through to one of the other strategies... */
+        case ASB_DISCARD_OLDER_PRI:
+                if (self == 0 && peer == 1) {
+                        rv = 1;
+                        break;
+                }
+                if (self == 1 && peer == 0) {
+                        rv = -1;
+                        break;
+                }
+                /* Else fall through to one of the other strategies... */
+                dev_warn(DEV, "Discard younger/older primary did not found a decision\n"
+                     "Using discard-least-changes instead\n");
+        case ASB_DISCARD_ZERO_CHG:
+                if (ch_peer == 0 && ch_self == 0) {
+                        rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+                                ? -1 : 1;
+                        break;
+                } else {
+                        if (ch_peer == 0) { rv =  1; break; }
+                        if (ch_self == 0) { rv = -1; break; }
+                }
+                if (mdev->net_conf->after_sb_0p == ASB_DISCARD_ZERO_CHG)
+                        break;
+        case ASB_DISCARD_LEAST_CHG:
+                if      (ch_self < ch_peer)
+                        rv = -1;
+                else if (ch_self > ch_peer)
+                        rv =  1;
+                else /* ( ch_self == ch_peer ) */
+                     /* Well, then use something else. */
+                        rv = test_bit(DISCARD_CONCURRENT, &mdev->flags)
+                                ? -1 : 1;
+                break;
+        case ASB_DISCARD_LOCAL:
+                rv = -1;
+                break;
+        case ASB_DISCARD_REMOTE:
+                rv =  1;
+        }
+
+        return rv;
+}
+
+static int drbd_asb_recover_1p(struct drbd_conf *mdev) __must_hold(local)
+{
+        int self, peer, hg, rv = -100;
+
+        self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+        peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+        switch (mdev->net_conf->after_sb_1p) {
+        case ASB_DISCARD_YOUNGER_PRI:
+        case ASB_DISCARD_OLDER_PRI:
+        case ASB_DISCARD_LEAST_CHG:
+        case ASB_DISCARD_LOCAL:
+        case ASB_DISCARD_REMOTE:
+                dev_err(DEV, "Configuration error.\n");
+                break;
+        case ASB_DISCONNECT:
+                break;
+        case ASB_CONSENSUS:
+                hg = drbd_asb_recover_0p(mdev);
+                if (hg == -1 && mdev->state.role == R_SECONDARY)
+                        rv = hg;
+                if (hg == 1  && mdev->state.role == R_PRIMARY)
+                        rv = hg;
+                break;
+        case ASB_VIOLENTLY:
+                rv = drbd_asb_recover_0p(mdev);
+                break;
+        case ASB_DISCARD_SECONDARY:
+                return mdev->state.role == R_PRIMARY ? 1 : -1;
+        case ASB_CALL_HELPER:
+                hg = drbd_asb_recover_0p(mdev);
+                if (hg == -1 && mdev->state.role == R_PRIMARY) {
+                        self = drbd_set_role(mdev, R_SECONDARY, 0);
+                         /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+                          * we might be here in C_WF_REPORT_PARAMS which is transient.
+                          * we do not need to wait for the after state change work either. */
+                        self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+                        if (self != SS_SUCCESS) {
+                                drbd_khelper(mdev, "pri-lost-after-sb");
+                        } else {
+                                dev_warn(DEV, "Successfully gave up primary role.\n");
+                                rv = hg;
+                        }
+                } else
+                        rv = hg;
+        }
+
+        return rv;
+}
+
+static int drbd_asb_recover_2p(struct drbd_conf *mdev) __must_hold(local)
+{
+        int self, peer, hg, rv = -100;
+
+        self = mdev->ldev->md.uuid[UI_BITMAP] & 1;
+        peer = mdev->p_uuid[UI_BITMAP] & 1;
+
+        switch (mdev->net_conf->after_sb_2p) {
+        case ASB_DISCARD_YOUNGER_PRI:
+        case ASB_DISCARD_OLDER_PRI:
+        case ASB_DISCARD_LEAST_CHG:
+        case ASB_DISCARD_LOCAL:
+        case ASB_DISCARD_REMOTE:
+        case ASB_CONSENSUS:
+        case ASB_DISCARD_SECONDARY:
+                dev_err(DEV, "Configuration error.\n");
+                break;
+        case ASB_VIOLENTLY:
+                rv = drbd_asb_recover_0p(mdev);
+                break;
+        case ASB_DISCONNECT:
+                break;
+        case ASB_CALL_HELPER:
+                hg = drbd_asb_recover_0p(mdev);
+                if (hg == -1) {
+                         /* drbd_change_state() does not sleep while in SS_IN_TRANSIENT_STATE,
+                          * we might be here in C_WF_REPORT_PARAMS which is transient.
+                          * we do not need to wait for the after state change work either. */
+                        self = drbd_change_state(mdev, CS_VERBOSE, NS(role, R_SECONDARY));
+                        if (self != SS_SUCCESS) {
+                                drbd_khelper(mdev, "pri-lost-after-sb");
+                        } else {
+                                dev_warn(DEV, "Successfully gave up primary role.\n");
+                                rv = hg;
+                        }
+                } else
+                        rv = hg;
+        }
+
+        return rv;
+}
+
+static void drbd_uuid_dump(struct drbd_conf *mdev, char *text, u64 *uuid,
+                           u64 bits, u64 flags)
+{
+        if (!uuid) {
+                dev_info(DEV, "%s uuid info vanished while I was looking!\n", text);
+                return;
+        }
+        dev_info(DEV, "%s %016llX:%016llX:%016llX:%016llX bits:%llu flags:%llX\n",
+             text,
+             (unsigned long long)uuid[UI_CURRENT],
+             (unsigned long long)uuid[UI_BITMAP],
+             (unsigned long long)uuid[UI_HISTORY_START],
+             (unsigned long long)uuid[UI_HISTORY_END],
+             (unsigned long long)bits,
+             (unsigned long long)flags);
+}
+
+/*
+  100   after split brain try auto recover
+    2   C_SYNC_SOURCE set BitMap
+    1   C_SYNC_SOURCE use BitMap
+    0   no Sync
+   -1   C_SYNC_TARGET use BitMap
+   -2   C_SYNC_TARGET set BitMap
+ -100   after split brain, disconnect
+-1000   unrelated data
+ */
+static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(local)
+{
+        u64 self, peer;
+        int i, j;
+
+        self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+        peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+
+        *rule_nr = 10;
+        if (self == UUID_JUST_CREATED && peer == UUID_JUST_CREATED)
+                return 0;
+
+        *rule_nr = 20;
+        if ((self == UUID_JUST_CREATED || self == (u64)0) &&
+             peer != UUID_JUST_CREATED)
+                return -2;
+
+        *rule_nr = 30;
+        if (self != UUID_JUST_CREATED &&
+            (peer == UUID_JUST_CREATED || peer == (u64)0))
+                return 2;
+
+        if (self == peer) {
+                int rct, dc; /* roles at crash time */
+
+                if (mdev->p_uuid[UI_BITMAP] == (u64)0 && mdev->ldev->md.uuid[UI_BITMAP] != (u64)0) {
+
+                        if (mdev->agreed_pro_version < 91)
+                                return -1001;
+
+                        if ((mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
+                            (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1))) {
+                                dev_info(DEV, "was SyncSource, missed the resync finished event, corrected myself:\n");
+                                drbd_uuid_set_bm(mdev, 0UL);
+
+                                drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+                                               mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+                                *rule_nr = 34;
+                        } else {
+                                dev_info(DEV, "was SyncSource (peer failed to write sync_uuid)\n");
+                                *rule_nr = 36;
+                        }
+
+                        return 1;
+                }
+
+                if (mdev->ldev->md.uuid[UI_BITMAP] == (u64)0 && mdev->p_uuid[UI_BITMAP] != (u64)0) {
+
+                        if (mdev->agreed_pro_version < 91)
+                                return -1001;
+
+                        if ((mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_BITMAP] & ~((u64)1)) &&
+                            (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1))) {
+                                dev_info(DEV, "was SyncTarget, peer missed the resync finished event, corrected peer:\n");
+
+                                mdev->p_uuid[UI_HISTORY_START + 1] = mdev->p_uuid[UI_HISTORY_START];
+                                mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_BITMAP];
+                                mdev->p_uuid[UI_BITMAP] = 0UL;
+
+                                drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+                                *rule_nr = 35;
+                        } else {
+                                dev_info(DEV, "was SyncTarget (failed to write sync_uuid)\n");
+                                *rule_nr = 37;
+                        }
+
+                        return -1;
+                }
+
+                /* Common power [off|failure] */
+                rct = (test_bit(CRASHED_PRIMARY, &mdev->flags) ? 1 : 0) +
+                        (mdev->p_uuid[UI_FLAGS] & 2);
+                /* lowest bit is set when we were primary,
+                 * next bit (weight 2) is set when peer was primary */
+                *rule_nr = 40;
+
+                switch (rct) {
+                case 0: /* !self_pri && !peer_pri */ return 0;
+                case 1: /*  self_pri && !peer_pri */ return 1;
+                case 2: /* !self_pri &&  peer_pri */ return -1;
+                case 3: /*  self_pri &&  peer_pri */
+                        dc = test_bit(DISCARD_CONCURRENT, &mdev->flags);
+                        return dc ? -1 : 1;
+                }
+        }
+
+        *rule_nr = 50;
+        peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+        if (self == peer)
+                return -1;
+
+        *rule_nr = 51;
+        peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
+        if (self == peer) {
+                self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
+                peer = mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1);
+                if (self == peer) {
+                        /* The last P_SYNC_UUID did not get though. Undo the last start of
+                           resync as sync source modifications of the peer's UUIDs. */
+
+                        if (mdev->agreed_pro_version < 91)
+                                return -1001;
+
+                        mdev->p_uuid[UI_BITMAP] = mdev->p_uuid[UI_HISTORY_START];
+                        mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_HISTORY_START + 1];
+                        return -1;
+                }
+        }
+
+        *rule_nr = 60;
+        self = mdev->ldev->md.uuid[UI_CURRENT] & ~((u64)1);
+        for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+                peer = mdev->p_uuid[i] & ~((u64)1);
+                if (self == peer)
+                        return -2;
+        }
+
+        *rule_nr = 70;
+        self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+        peer = mdev->p_uuid[UI_CURRENT] & ~((u64)1);
+        if (self == peer)
+                return 1;
+
+        *rule_nr = 71;
+        self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
+        if (self == peer) {
+                self = mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1);
+                peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
+                if (self == peer) {
+                        /* The last P_SYNC_UUID did not get though. Undo the last start of
+                           resync as sync source modifications of our UUIDs. */
+
+                        if (mdev->agreed_pro_version < 91)
+                                return -1001;
+
+                        _drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_HISTORY_START]);
+                        _drbd_uuid_set(mdev, UI_HISTORY_START, mdev->ldev->md.uuid[UI_HISTORY_START + 1]);
+
+                        dev_info(DEV, "Undid last start of resync:\n");
+
+                        drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
+                                       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
+
+                        return 1;
+                }
+        }
+
+
+        *rule_nr = 80;
+        for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+                self = mdev->ldev->md.uuid[i] & ~((u64)1);
+                if (self == peer)
+                        return 2;
+        }
+
+        *rule_nr = 90;
+        self = mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1);
+        peer = mdev->p_uuid[UI_BITMAP] & ~((u64)1);
+        if (self == peer && self != ((u64)0))
+                return 100;
+
+        *rule_nr = 100;
+        for (i = UI_HISTORY_START; i <= UI_HISTORY_END; i++) {
+                self = mdev->ldev->md.uuid[i] & ~((u64)1);
+                for (j = UI_HISTORY_START; j <= UI_HISTORY_END; j++) {
+                        peer = mdev->p_uuid[j] & ~((u64)1);
+                        if (self == peer)
+                                return -100;
+                }
+        }
+
+        return -1000;
+}
+
+/* drbd_sync_handshake() returns the new conn state on success, or
+   CONN_MASK (-1) on failure.
+ */
+static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_role peer_role,
+                                           enum drbd_disk_state peer_disk) __must_hold(local)
+{
+        int hg, rule_nr;
+        enum drbd_conns rv = C_MASK;
+        enum drbd_disk_state mydisk;
+
+        mydisk = mdev->state.disk;
+        if (mydisk == D_NEGOTIATING)
+                mydisk = mdev->new_state_tmp.disk;
+
+        dev_info(DEV, "drbd_sync_handshake:\n");
+        drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid, mdev->comm_bm_set, 0);
+        drbd_uuid_dump(mdev, "peer", mdev->p_uuid,
+                       mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
+        hg = drbd_uuid_compare(mdev, &rule_nr);
+
+        dev_info(DEV, "uuid_compare()=%d by rule %d\n", hg, rule_nr);
+
+        if (hg == -1000) {
+                dev_alert(DEV, "Unrelated data, aborting!\n");
+                return C_MASK;
+        }
+        if (hg == -1001) {
+                dev_alert(DEV, "To resolve this both sides have to support at least protocol\n");
+                return C_MASK;
+        }
+
+        if    ((mydisk == D_INCONSISTENT && peer_disk > D_INCONSISTENT) ||
+            (peer_disk == D_INCONSISTENT && mydisk    > D_INCONSISTENT)) {
+                int f = (hg == -100) || abs(hg) == 2;
+                hg = mydisk > D_INCONSISTENT ? 1 : -1;
+                if (f)
+                        hg = hg*2;
+                dev_info(DEV, "Becoming sync %s due to disk states.\n",
+                     hg > 0 ? "source" : "target");
+        }
+
+        if (hg == 100 || (hg == -100 && mdev->net_conf->always_asbp)) {
+                int pcount = (mdev->state.role == R_PRIMARY)
+                           + (peer_role == R_PRIMARY);
+                int forced = (hg == -100);
+
+                switch (pcount) {
+                case 0:
+                        hg = drbd_asb_recover_0p(mdev);
+                        break;
+                case 1:
+                        hg = drbd_asb_recover_1p(mdev);
+                        break;
+                case 2:
+                        hg = drbd_asb_recover_2p(mdev);
+                        break;
+                }
+                if (abs(hg) < 100) {
+                        dev_warn(DEV, "Split-Brain detected, %d primaries, "
+                             "automatically solved. Sync from %s node\n",
+                             pcount, (hg < 0) ? "peer" : "this");
+                        if (forced) {
+                                dev_warn(DEV, "Doing a full sync, since"
+                                     " UUIDs where ambiguous.\n");
+                                hg = hg*2;
+                        }
+                }
+        }
+
+        if (hg == -100) {
+                if (mdev->net_conf->want_lose && !(mdev->p_uuid[UI_FLAGS]&1))
+                        hg = -1;
+                if (!mdev->net_conf->want_lose && (mdev->p_uuid[UI_FLAGS]&1))
+                        hg = 1;
+
+                if (abs(hg) < 100)
+                        dev_warn(DEV, "Split-Brain detected, manually solved. "
+                             "Sync from %s node\n",
+                             (hg < 0) ? "peer" : "this");
+        }
+
+        if (hg == -100) {
+                dev_alert(DEV, "Split-Brain detected, dropping connection!\n");
+                drbd_khelper(mdev, "split-brain");
+                return C_MASK;
+        }
+
+        if (hg > 0 && mydisk <= D_INCONSISTENT) {
+                dev_err(DEV, "I shall become SyncSource, but I am inconsistent!\n");
+                return C_MASK;
+        }
+
+        if (hg < 0 && /* by intention we do not use mydisk here. */
+            mdev->state.role == R_PRIMARY && mdev->state.disk >= D_CONSISTENT) {
+                switch (mdev->net_conf->rr_conflict) {
+                case ASB_CALL_HELPER:
+                        drbd_khelper(mdev, "pri-lost");
+                        /* fall through */
+                case ASB_DISCONNECT:
+                        dev_err(DEV, "I shall become SyncTarget, but I am primary!\n");
+                        return C_MASK;
+                case ASB_VIOLENTLY:
+                        dev_warn(DEV, "Becoming SyncTarget, violating the stable-data"
+                             "assumption\n");
+                }
+        }
+
+        if (abs(hg) >= 2) {
+                dev_info(DEV, "Writing the whole bitmap, full sync required after drbd_sync_handshake.\n");
+                if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake"))
+                        return C_MASK;
+        }
+
+        if (hg > 0) { /* become sync source. */
+                rv = C_WF_BITMAP_S;
+        } else if (hg < 0) { /* become sync target */
+                rv = C_WF_BITMAP_T;
+        } else {
+                rv = C_CONNECTED;
+                if (drbd_bm_total_weight(mdev)) {
+                        dev_info(DEV, "No resync, but %lu bits in bitmap!\n",
+                             drbd_bm_total_weight(mdev));
+                }
+        }
+
+        return rv;
+}
+
+/* returns 1 if invalid */
+static int cmp_after_sb(enum drbd_after_sb_p peer, enum drbd_after_sb_p self)
+{
+        /* ASB_DISCARD_REMOTE - ASB_DISCARD_LOCAL is valid */
+        if ((peer == ASB_DISCARD_REMOTE && self == ASB_DISCARD_LOCAL) ||
+            (self == ASB_DISCARD_REMOTE && peer == ASB_DISCARD_LOCAL))
+                return 0;
+
+        /* any other things with ASB_DISCARD_REMOTE or ASB_DISCARD_LOCAL are invalid */
+        if (peer == ASB_DISCARD_REMOTE || peer == ASB_DISCARD_LOCAL ||
+            self == ASB_DISCARD_REMOTE || self == ASB_DISCARD_LOCAL)
+                return 1;
+
+        /* everything else is valid if they are equal on both sides. */
+        if (peer == self)
+                return 0;
+
+        /* everything es is invalid. */
+        return 1;
+}
+
+static int receive_protocol(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_protocol *p = (struct p_protocol *)h;
+        int header_size, data_size;
+        int p_proto, p_after_sb_0p, p_after_sb_1p, p_after_sb_2p;
+        int p_want_lose, p_two_primaries;
+        char p_integrity_alg[SHARED_SECRET_MAX] = "";
+
+        header_size = sizeof(*p) - sizeof(*h);
+        data_size   = h->length  - header_size;
+
+        if (drbd_recv(mdev, h->payload, header_size) != header_size)
+                return FALSE;
+
+        p_proto         = be32_to_cpu(p->protocol);
+        p_after_sb_0p   = be32_to_cpu(p->after_sb_0p);
+        p_after_sb_1p   = be32_to_cpu(p->after_sb_1p);
+        p_after_sb_2p   = be32_to_cpu(p->after_sb_2p);
+        p_want_lose     = be32_to_cpu(p->want_lose);
+        p_two_primaries = be32_to_cpu(p->two_primaries);
+
+        if (p_proto != mdev->net_conf->wire_protocol) {
+                dev_err(DEV, "incompatible communication protocols\n");
+                goto disconnect;
+        }
+
+        if (cmp_after_sb(p_after_sb_0p, mdev->net_conf->after_sb_0p)) {
+                dev_err(DEV, "incompatible after-sb-0pri settings\n");
+                goto disconnect;
+        }
+
+        if (cmp_after_sb(p_after_sb_1p, mdev->net_conf->after_sb_1p)) {
+                dev_err(DEV, "incompatible after-sb-1pri settings\n");
+                goto disconnect;
+        }
+
+        if (cmp_after_sb(p_after_sb_2p, mdev->net_conf->after_sb_2p)) {
+                dev_err(DEV, "incompatible after-sb-2pri settings\n");
+                goto disconnect;
+        }
+
+        if (p_want_lose && mdev->net_conf->want_lose) {
+                dev_err(DEV, "both sides have the 'want_lose' flag set\n");
+                goto disconnect;
+        }
+
+        if (p_two_primaries != mdev->net_conf->two_primaries) {
+                dev_err(DEV, "incompatible setting of the two-primaries options\n");
+                goto disconnect;
+        }
+
+        if (mdev->agreed_pro_version >= 87) {
+                unsigned char *my_alg = mdev->net_conf->integrity_alg;
+
+                if (drbd_recv(mdev, p_integrity_alg, data_size) != data_size)
+                        return FALSE;
+
+                p_integrity_alg[SHARED_SECRET_MAX-1] = 0;
+                if (strcmp(p_integrity_alg, my_alg)) {
+                        dev_err(DEV, "incompatible setting of the data-integrity-alg\n");
+                        goto disconnect;
+                }
+                dev_info(DEV, "data-integrity-alg: %s\n",
+                     my_alg[0] ? my_alg : (unsigned char *)"<not-used>");
+        }
+
+        return TRUE;
+
+disconnect:
+        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+        return FALSE;
+}
+
+/* helper function
+ * input: alg name, feature name
+ * return: NULL (alg name was "")
+ *         ERR_PTR(error) if something goes wrong
+ *         or the crypto hash ptr, if it worked out ok. */
+struct crypto_hash *drbd_crypto_alloc_digest_safe(const struct drbd_conf *mdev,
+                const char *alg, const char *name)
+{
+        struct crypto_hash *tfm;
+
+        if (!alg[0])
+                return NULL;
+
+        tfm = crypto_alloc_hash(alg, 0, CRYPTO_ALG_ASYNC);
+        if (IS_ERR(tfm)) {
+                dev_err(DEV, "Can not allocate \"%s\" as %s (reason: %ld)\n",
+                        alg, name, PTR_ERR(tfm));
+                return tfm;
+        }
+        if (!drbd_crypto_is_hash(crypto_hash_tfm(tfm))) {
+                crypto_free_hash(tfm);
+                dev_err(DEV, "\"%s\" is not a digest (%s)\n", alg, name);
+                return ERR_PTR(-EINVAL);
+        }
+        return tfm;
+}
+
+static int receive_SyncParam(struct drbd_conf *mdev, struct p_header *h)
+{
+        int ok = TRUE;
+        struct p_rs_param_89 *p = (struct p_rs_param_89 *)h;
+        unsigned int header_size, data_size, exp_max_sz;
+        struct crypto_hash *verify_tfm = NULL;
+        struct crypto_hash *csums_tfm = NULL;
+        const int apv = mdev->agreed_pro_version;
+
+        exp_max_sz  = apv <= 87 ? sizeof(struct p_rs_param)
+                    : apv == 88 ? sizeof(struct p_rs_param)
+                                        + SHARED_SECRET_MAX
+                    : /* 89 */    sizeof(struct p_rs_param_89);
+
+        if (h->length > exp_max_sz) {
+                dev_err(DEV, "SyncParam packet too long: received %u, expected <= %u bytes\n",
+                    h->length, exp_max_sz);
+                return FALSE;
+        }
+
+        if (apv <= 88) {
+                header_size = sizeof(struct p_rs_param) - sizeof(*h);
+                data_size   = h->length  - header_size;
+        } else /* apv >= 89 */ {
+                header_size = sizeof(struct p_rs_param_89) - sizeof(*h);
+                data_size   = h->length  - header_size;
+                D_ASSERT(data_size == 0);
+        }
+
+        /* initialize verify_alg and csums_alg */
+        memset(p->verify_alg, 0, 2 * SHARED_SECRET_MAX);
+
+        if (drbd_recv(mdev, h->payload, header_size) != header_size)
+                return FALSE;
+
+        mdev->sync_conf.rate      = be32_to_cpu(p->rate);
+
+        if (apv >= 88) {
+                if (apv == 88) {
+                        if (data_size > SHARED_SECRET_MAX) {
+                                dev_err(DEV, "verify-alg too long, "
+                                    "peer wants %u, accepting only %u byte\n",
+                                                data_size, SHARED_SECRET_MAX);
+                                return FALSE;
+                        }
+
+                        if (drbd_recv(mdev, p->verify_alg, data_size) != data_size)
+                                return FALSE;
+
+                        /* we expect NUL terminated string */
+                        /* but just in case someone tries to be evil */
+                        D_ASSERT(p->verify_alg[data_size-1] == 0);
+                        p->verify_alg[data_size-1] = 0;
+
+                } else /* apv >= 89 */ {
+                        /* we still expect NUL terminated strings */
+                        /* but just in case someone tries to be evil */
+                        D_ASSERT(p->verify_alg[SHARED_SECRET_MAX-1] == 0);
+                        D_ASSERT(p->csums_alg[SHARED_SECRET_MAX-1] == 0);
+                        p->verify_alg[SHARED_SECRET_MAX-1] = 0;
+                        p->csums_alg[SHARED_SECRET_MAX-1] = 0;
+                }
+
+                if (strcmp(mdev->sync_conf.verify_alg, p->verify_alg)) {
+                        if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+                                dev_err(DEV, "Different verify-alg settings. me=\"%s\" peer=\"%s\"\n",
+                                    mdev->sync_conf.verify_alg, p->verify_alg);
+                                goto disconnect;
+                        }
+                        verify_tfm = drbd_crypto_alloc_digest_safe(mdev,
+                                        p->verify_alg, "verify-alg");
+                        if (IS_ERR(verify_tfm)) {
+                                verify_tfm = NULL;
+                                goto disconnect;
+                        }
+                }
+
+                if (apv >= 89 && strcmp(mdev->sync_conf.csums_alg, p->csums_alg)) {
+                        if (mdev->state.conn == C_WF_REPORT_PARAMS) {
+                                dev_err(DEV, "Different csums-alg settings. me=\"%s\" peer=\"%s\"\n",
+                                    mdev->sync_conf.csums_alg, p->csums_alg);
+                                goto disconnect;
+                        }
+                        csums_tfm = drbd_crypto_alloc_digest_safe(mdev,
+                                        p->csums_alg, "csums-alg");
+                        if (IS_ERR(csums_tfm)) {
+                                csums_tfm = NULL;
+                                goto disconnect;
+                        }
+                }
+
+
+                spin_lock(&mdev->peer_seq_lock);
+                /* lock against drbd_nl_syncer_conf() */
+                if (verify_tfm) {
+                        strcpy(mdev->sync_conf.verify_alg, p->verify_alg);
+                        mdev->sync_conf.verify_alg_len = strlen(p->verify_alg) + 1;
+                        crypto_free_hash(mdev->verify_tfm);
+                        mdev->verify_tfm = verify_tfm;
+                        dev_info(DEV, "using verify-alg: \"%s\"\n", p->verify_alg);
+                }
+                if (csums_tfm) {
+                        strcpy(mdev->sync_conf.csums_alg, p->csums_alg);
+                        mdev->sync_conf.csums_alg_len = strlen(p->csums_alg) + 1;
+                        crypto_free_hash(mdev->csums_tfm);
+                        mdev->csums_tfm = csums_tfm;
+                        dev_info(DEV, "using csums-alg: \"%s\"\n", p->csums_alg);
+                }
+                spin_unlock(&mdev->peer_seq_lock);
+        }
+
+        return ok;
+disconnect:
+        /* just for completeness: actually not needed,
+         * as this is not reached if csums_tfm was ok. */
+        crypto_free_hash(csums_tfm);
+        /* but free the verify_tfm again, if csums_tfm did not work out */
+        crypto_free_hash(verify_tfm);
+        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+        return FALSE;
+}
+
+static void drbd_setup_order_type(struct drbd_conf *mdev, int peer)
+{
+        /* sorry, we currently have no working implementation
+         * of distributed TCQ */
+}
+
+/* warn if the arguments differ by more than 12.5% */
+static void warn_if_differ_considerably(struct drbd_conf *mdev,
+        const char *s, sector_t a, sector_t b)
+{
+        sector_t d;
+        if (a == 0 || b == 0)
+                return;
+        d = (a > b) ? (a - b) : (b - a);
+        if (d > (a>>3) || d > (b>>3))
+                dev_warn(DEV, "Considerable difference in %s: %llus vs. %llus\n", s,
+                     (unsigned long long)a, (unsigned long long)b);
+}
+
+static int receive_sizes(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_sizes *p = (struct p_sizes *)h;
+        enum determine_dev_size dd = unchanged;
+        unsigned int max_seg_s;
+        sector_t p_size, p_usize, my_usize;
+        int ldsc = 0; /* local disk size changed */
+        enum drbd_conns nconn;
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+        if (drbd_recv(mdev, h->payload, h->length) != h->length)
+                return FALSE;
+
+        p_size = be64_to_cpu(p->d_size);
+        p_usize = be64_to_cpu(p->u_size);
+
+        if (p_size == 0 && mdev->state.disk == D_DISKLESS) {
+                dev_err(DEV, "some backing storage is needed\n");
+                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                return FALSE;
+        }
+
+        /* just store the peer's disk size for now.
+         * we still need to figure out whether we accept that. */
+        mdev->p_size = p_size;
+
+#define min_not_zero(l, r) (l == 0) ? r : ((r == 0) ? l : min(l, r))
+        if (get_ldev(mdev)) {
+                warn_if_differ_considerably(mdev, "lower level device sizes",
+                           p_size, drbd_get_max_capacity(mdev->ldev));
+                warn_if_differ_considerably(mdev, "user requested size",
+                                            p_usize, mdev->ldev->dc.disk_size);
+
+                /* if this is the first connect, or an otherwise expected
+                 * param exchange, choose the minimum */
+                if (mdev->state.conn == C_WF_REPORT_PARAMS)
+                        p_usize = min_not_zero((sector_t)mdev->ldev->dc.disk_size,
+                                             p_usize);
+
+                my_usize = mdev->ldev->dc.disk_size;
+
+                if (mdev->ldev->dc.disk_size != p_usize) {
+                        mdev->ldev->dc.disk_size = p_usize;
+                        dev_info(DEV, "Peer sets u_size to %lu sectors\n",
+                             (unsigned long)mdev->ldev->dc.disk_size);
+                }
+
+                /* Never shrink a device with usable data during connect.
+                   But allow online shrinking if we are connected. */
+                if (drbd_new_dev_size(mdev, mdev->ldev) <
+                   drbd_get_capacity(mdev->this_bdev) &&
+                   mdev->state.disk >= D_OUTDATED &&
+                   mdev->state.conn < C_CONNECTED) {
+                        dev_err(DEV, "The peer's disk size is too small!\n");
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                        mdev->ldev->dc.disk_size = my_usize;
+                        put_ldev(mdev);
+                        return FALSE;
+                }
+                put_ldev(mdev);
+        }
+#undef min_not_zero
+
+        if (get_ldev(mdev)) {
+                dd = drbd_determin_dev_size(mdev);
+                put_ldev(mdev);
+                if (dd == dev_size_error)
+                        return FALSE;
+                drbd_md_sync(mdev);
+        } else {
+                /* I am diskless, need to accept the peer's size. */
+                drbd_set_my_capacity(mdev, p_size);
+        }
+
+        if (mdev->p_uuid && mdev->state.conn <= C_CONNECTED && get_ldev(mdev)) {
+                nconn = drbd_sync_handshake(mdev,
+                                mdev->state.peer, mdev->state.pdsk);
+                put_ldev(mdev);
+
+                if (nconn == C_MASK) {
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                        return FALSE;
+                }
+
+                if (drbd_request_state(mdev, NS(conn, nconn)) < SS_SUCCESS) {
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                        return FALSE;
+                }
+        }
+
+        if (get_ldev(mdev)) {
+                if (mdev->ldev->known_size != drbd_get_capacity(mdev->ldev->backing_bdev)) {
+                        mdev->ldev->known_size = drbd_get_capacity(mdev->ldev->backing_bdev);
+                        ldsc = 1;
+                }
+
+                max_seg_s = be32_to_cpu(p->max_segment_size);
+                if (max_seg_s != queue_max_segment_size(mdev->rq_queue))
+                        drbd_setup_queue_param(mdev, max_seg_s);
+
+                drbd_setup_order_type(mdev, be32_to_cpu(p->queue_order_type));
+                put_ldev(mdev);
+        }
+
+        if (mdev->state.conn > C_WF_REPORT_PARAMS) {
+                if (be64_to_cpu(p->c_size) !=
+                    drbd_get_capacity(mdev->this_bdev) || ldsc) {
+                        /* we have different sizes, probably peer
+                         * needs to know my new size... */
+                        drbd_send_sizes(mdev, 0);
+                }
+                if (test_and_clear_bit(RESIZE_PENDING, &mdev->flags) ||
+                    (dd == grew && mdev->state.conn == C_CONNECTED)) {
+                        if (mdev->state.pdsk >= D_INCONSISTENT &&
+                            mdev->state.disk >= D_INCONSISTENT)
+                                resync_after_online_grow(mdev);
+                        else
+                                set_bit(RESYNC_AFTER_NEG, &mdev->flags);
+                }
+        }
+
+        return TRUE;
+}
+
+static int receive_uuids(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_uuids *p = (struct p_uuids *)h;
+        u64 *p_uuid;
+        int i;
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+        if (drbd_recv(mdev, h->payload, h->length) != h->length)
+                return FALSE;
+
+        p_uuid = kmalloc(sizeof(u64)*UI_EXTENDED_SIZE, GFP_NOIO);
+
+        for (i = UI_CURRENT; i < UI_EXTENDED_SIZE; i++)
+                p_uuid[i] = be64_to_cpu(p->uuid[i]);
+
+        kfree(mdev->p_uuid);
+        mdev->p_uuid = p_uuid;
+
+        if (mdev->state.conn < C_CONNECTED &&
+            mdev->state.disk < D_INCONSISTENT &&
+            mdev->state.role == R_PRIMARY &&
+            (mdev->ed_uuid & ~((u64)1)) != (p_uuid[UI_CURRENT] & ~((u64)1))) {
+                dev_err(DEV, "Can only connect to data with current UUID=%016llX\n",
+                    (unsigned long long)mdev->ed_uuid);
+                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                return FALSE;
+        }
+
+        if (get_ldev(mdev)) {
+                int skip_initial_sync =
+                        mdev->state.conn == C_CONNECTED &&
+                        mdev->agreed_pro_version >= 90 &&
+                        mdev->ldev->md.uuid[UI_CURRENT] == UUID_JUST_CREATED &&
+                        (p_uuid[UI_FLAGS] & 8);
+                if (skip_initial_sync) {
+                        dev_info(DEV, "Accepted new current UUID, preparing to skip initial sync\n");
+                        drbd_bitmap_io(mdev, &drbd_bmio_clear_n_write,
+                                        "clear_n_write from receive_uuids");
+                        _drbd_uuid_set(mdev, UI_CURRENT, p_uuid[UI_CURRENT]);
+                        _drbd_uuid_set(mdev, UI_BITMAP, 0);
+                        _drbd_set_state(_NS2(mdev, disk, D_UP_TO_DATE, pdsk, D_UP_TO_DATE),
+                                        CS_VERBOSE, NULL);
+                        drbd_md_sync(mdev);
+                }
+                put_ldev(mdev);
+        }
+
+        /* Before we test for the disk state, we should wait until an eventually
+           ongoing cluster wide state change is finished. That is important if
+           we are primary and are detaching from our disk. We need to see the
+           new disk state... */
+        wait_event(mdev->misc_wait, !test_bit(CLUSTER_ST_CHANGE, &mdev->flags));
+        if (mdev->state.conn >= C_CONNECTED && mdev->state.disk < D_INCONSISTENT)
+                drbd_set_ed_uuid(mdev, p_uuid[UI_CURRENT]);
+
+        return TRUE;
+}
+
+/**
+ * convert_state() - Converts the peer's view of the cluster state to our point of view
+ * @ps:         The state as seen by the peer.
+ */
+static union drbd_state convert_state(union drbd_state ps)
+{
+        union drbd_state ms;
+
+        static enum drbd_conns c_tab[] = {
+                [C_CONNECTED] = C_CONNECTED,
+
+                [C_STARTING_SYNC_S] = C_STARTING_SYNC_T,
+                [C_STARTING_SYNC_T] = C_STARTING_SYNC_S,
+                [C_DISCONNECTING] = C_TEAR_DOWN, /* C_NETWORK_FAILURE, */
+                [C_VERIFY_S]       = C_VERIFY_T,
+                [C_MASK]   = C_MASK,
+        };
+
+        ms.i = ps.i;
+
+        ms.conn = c_tab[ps.conn];
+        ms.peer = ps.role;
+        ms.role = ps.peer;
+        ms.pdsk = ps.disk;
+        ms.disk = ps.pdsk;
+        ms.peer_isp = (ps.aftr_isp | ps.user_isp);
+
+        return ms;
+}
+
+static int receive_req_state(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_req_state *p = (struct p_req_state *)h;
+        union drbd_state mask, val;
+        int rv;
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+        if (drbd_recv(mdev, h->payload, h->length) != h->length)
+                return FALSE;
+
+        mask.i = be32_to_cpu(p->mask);
+        val.i = be32_to_cpu(p->val);
+
+        if (test_bit(DISCARD_CONCURRENT, &mdev->flags) &&
+            test_bit(CLUSTER_ST_CHANGE, &mdev->flags)) {
+                drbd_send_sr_reply(mdev, SS_CONCURRENT_ST_CHG);
+                return TRUE;
+        }
+
+        mask = convert_state(mask);
+        val = convert_state(val);
+
+        rv = drbd_change_state(mdev, CS_VERBOSE, mask, val);
+
+        drbd_send_sr_reply(mdev, rv);
+        drbd_md_sync(mdev);
+
+        return TRUE;
+}
+
+static int receive_state(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_state *p = (struct p_state *)h;
+        enum drbd_conns nconn, oconn;
+        union drbd_state ns, peer_state;
+        enum drbd_disk_state real_peer_disk;
+        int rv;
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h)))
+                return FALSE;
+
+        if (drbd_recv(mdev, h->payload, h->length) != h->length)
+                return FALSE;
+
+        peer_state.i = be32_to_cpu(p->state);
+
+        real_peer_disk = peer_state.disk;
+        if (peer_state.disk == D_NEGOTIATING) {
+                real_peer_disk = mdev->p_uuid[UI_FLAGS] & 4 ? D_INCONSISTENT : D_CONSISTENT;
+                dev_info(DEV, "real peer disk state = %s\n", drbd_disk_str(real_peer_disk));
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+ retry:
+        oconn = nconn = mdev->state.conn;
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (nconn == C_WF_REPORT_PARAMS)
+                nconn = C_CONNECTED;
+
+        if (mdev->p_uuid && peer_state.disk >= D_NEGOTIATING &&
+            get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                int cr; /* consider resync */
+
+                /* if we established a new connection */
+                cr  = (oconn < C_CONNECTED);
+                /* if we had an established connection
+                 * and one of the nodes newly attaches a disk */
+                cr |= (oconn == C_CONNECTED &&
+                       (peer_state.disk == D_NEGOTIATING ||
+                        mdev->state.disk == D_NEGOTIATING));
+                /* if we have both been inconsistent, and the peer has been
+                 * forced to be UpToDate with --overwrite-data */
+                cr |= test_bit(CONSIDER_RESYNC, &mdev->flags);
+                /* if we had been plain connected, and the admin requested to
+                 * start a sync by "invalidate" or "invalidate-remote" */
+                cr |= (oconn == C_CONNECTED &&
+                                (peer_state.conn >= C_STARTING_SYNC_S &&
+                                 peer_state.conn <= C_WF_BITMAP_T));
+
+                if (cr)
+                        nconn = drbd_sync_handshake(mdev, peer_state.role, real_peer_disk);
+
+                put_ldev(mdev);
+                if (nconn == C_MASK) {
+                        if (mdev->state.disk == D_NEGOTIATING) {
+                                drbd_force_state(mdev, NS(disk, D_DISKLESS));
+                                nconn = C_CONNECTED;
+                        } else if (peer_state.disk == D_NEGOTIATING) {
+                                dev_err(DEV, "Disk attach process on the peer node was aborted.\n");
+                                peer_state.disk = D_DISKLESS;
+                        } else {
+                                D_ASSERT(oconn == C_WF_REPORT_PARAMS);
+                                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                                return FALSE;
+                        }
+                }
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        if (mdev->state.conn != oconn)
+                goto retry;
+        clear_bit(CONSIDER_RESYNC, &mdev->flags);
+        ns.i = mdev->state.i;
+        ns.conn = nconn;
+        ns.peer = peer_state.role;
+        ns.pdsk = real_peer_disk;
+        ns.peer_isp = (peer_state.aftr_isp | peer_state.user_isp);
+        if ((nconn == C_CONNECTED || nconn == C_WF_BITMAP_S) && ns.disk == D_NEGOTIATING)
+                ns.disk = mdev->new_state_tmp.disk;
+
+        rv = _drbd_set_state(mdev, ns, CS_VERBOSE | CS_HARD, NULL);
+        ns = mdev->state;
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (rv < SS_SUCCESS) {
+                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                return FALSE;
+        }
+
+        if (oconn > C_WF_REPORT_PARAMS) {
+                if (nconn > C_CONNECTED && peer_state.conn <= C_CONNECTED &&
+                    peer_state.disk != D_NEGOTIATING ) {
+                        /* we want resync, peer has not yet decided to sync... */
+                        /* Nowadays only used when forcing a node into primary role and
+                           setting its disk to UpToDate with that */
+                        drbd_send_uuids(mdev);
+                        drbd_send_state(mdev);
+                }
+        }
+
+        mdev->net_conf->want_lose = 0;
+
+        drbd_md_sync(mdev); /* update connected indicator, la_size, ... */
+
+        return TRUE;
+}
+
+static int receive_sync_uuid(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_rs_uuid *p = (struct p_rs_uuid *)h;
+
+        wait_event(mdev->misc_wait,
+                   mdev->state.conn == C_WF_SYNC_UUID ||
+                   mdev->state.conn < C_CONNECTED ||
+                   mdev->state.disk < D_NEGOTIATING);
+
+        /* D_ASSERT( mdev->state.conn == C_WF_SYNC_UUID ); */
+
+        ERR_IF(h->length != (sizeof(*p)-sizeof(*h))) return FALSE;
+        if (drbd_recv(mdev, h->payload, h->length) != h->length)
+                return FALSE;
+
+        /* Here the _drbd_uuid_ functions are right, current should
+           _not_ be rotated into the history */
+        if (get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                _drbd_uuid_set(mdev, UI_CURRENT, be64_to_cpu(p->uuid));
+                _drbd_uuid_set(mdev, UI_BITMAP, 0UL);
+
+                drbd_start_resync(mdev, C_SYNC_TARGET);
+
+                put_ldev(mdev);
+        } else
+                dev_err(DEV, "Ignoring SyncUUID packet!\n");
+
+        return TRUE;
+}
+
+enum receive_bitmap_ret { OK, DONE, FAILED };
+
+static enum receive_bitmap_ret
+receive_bitmap_plain(struct drbd_conf *mdev, struct p_header *h,
+        unsigned long *buffer, struct bm_xfer_ctx *c)
+{
+        unsigned num_words = min_t(size_t, BM_PACKET_WORDS, c->bm_words - c->word_offset);
+        unsigned want = num_words * sizeof(long);
+
+        if (want != h->length) {
+                dev_err(DEV, "%s:want (%u) != h->length (%u)\n", __func__, want, h->length);
+                return FAILED;
+        }
+        if (want == 0)
+                return DONE;
+        if (drbd_recv(mdev, buffer, want) != want)
+                return FAILED;
+
+        drbd_bm_merge_lel(mdev, c->word_offset, num_words, buffer);
+
+        c->word_offset += num_words;
+        c->bit_offset = c->word_offset * BITS_PER_LONG;
+        if (c->bit_offset > c->bm_bits)
+                c->bit_offset = c->bm_bits;
+
+        return OK;
+}
+
+static enum receive_bitmap_ret
+recv_bm_rle_bits(struct drbd_conf *mdev,
+                struct p_compressed_bm *p,
+                struct bm_xfer_ctx *c)
+{
+        struct bitstream bs;
+        u64 look_ahead;
+        u64 rl;
+        u64 tmp;
+        unsigned long s = c->bit_offset;
+        unsigned long e;
+        int len = p->head.length - (sizeof(*p) - sizeof(p->head));
+        int toggle = DCBP_get_start(p);
+        int have;
+        int bits;
+
+        bitstream_init(&bs, p->code, len, DCBP_get_pad_bits(p));
+
+        bits = bitstream_get_bits(&bs, &look_ahead, 64);
+        if (bits < 0)
+                return FAILED;
+
+        for (have = bits; have > 0; s += rl, toggle = !toggle) {
+                bits = vli_decode_bits(&rl, look_ahead);
+                if (bits <= 0)
+                        return FAILED;
+
+                if (toggle) {
+                        e = s + rl -1;
+                        if (e >= c->bm_bits) {
+                                dev_err(DEV, "bitmap overflow (e:%lu) while decoding bm RLE packet\n", e);
+                                return FAILED;
+                        }
+                        _drbd_bm_set_bits(mdev, s, e);
+                }
+
+                if (have < bits) {
+                        dev_err(DEV, "bitmap decoding error: h:%d b:%d la:0x%08llx l:%u/%u\n",
+                                have, bits, look_ahead,
+                                (unsigned int)(bs.cur.b - p->code),
+                                (unsigned int)bs.buf_len);
+                        return FAILED;
+                }
+                look_ahead >>= bits;
+                have -= bits;
+
+                bits = bitstream_get_bits(&bs, &tmp, 64 - have);
+                if (bits < 0)
+                        return FAILED;
+                look_ahead |= tmp << have;
+                have += bits;
+        }
+
+        c->bit_offset = s;
+        bm_xfer_ctx_bit_to_word_offset(c);
+
+        return (s == c->bm_bits) ? DONE : OK;
+}
+
+static enum receive_bitmap_ret
+decode_bitmap_c(struct drbd_conf *mdev,
+                struct p_compressed_bm *p,
+                struct bm_xfer_ctx *c)
+{
+        if (DCBP_get_code(p) == RLE_VLI_Bits)
+                return recv_bm_rle_bits(mdev, p, c);
+
+        /* other variants had been implemented for evaluation,
+         * but have been dropped as this one turned out to be "best"
+         * during all our tests. */
+
+        dev_err(DEV, "receive_bitmap_c: unknown encoding %u\n", p->encoding);
+        drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+        return FAILED;
+}
+
+void INFO_bm_xfer_stats(struct drbd_conf *mdev,
+                const char *direction, struct bm_xfer_ctx *c)
+{
+        /* what would it take to transfer it "plaintext" */
+        unsigned plain = sizeof(struct p_header) *
+                ((c->bm_words+BM_PACKET_WORDS-1)/BM_PACKET_WORDS+1)
+                + c->bm_words * sizeof(long);
+        unsigned total = c->bytes[0] + c->bytes[1];
+        unsigned r;
+
+        /* total can not be zero. but just in case: */
+        if (total == 0)
+                return;
+
+        /* don't report if not compressed */
+        if (total >= plain)
+                return;
+
+        /* total < plain. check for overflow, still */
+        r = (total > UINT_MAX/1000) ? (total / (plain/1000))
+                                    : (1000 * total / plain);
+
+        if (r > 1000)
+                r = 1000;
+
+        r = 1000 - r;
+        dev_info(DEV, "%s bitmap stats [Bytes(packets)]: plain %u(%u), RLE %u(%u), "
+             "total %u; compression: %u.%u%%\n",
+                        direction,
+                        c->bytes[1], c->packets[1],
+                        c->bytes[0], c->packets[0],
+                        total, r/10, r % 10);
+}
+
+/* Since we are processing the bitfield from lower addresses to higher,
+   it does not matter if the process it in 32 bit chunks or 64 bit
+   chunks as long as it is little endian. (Understand it as byte stream,
+   beginning with the lowest byte...) If we would use big endian
+   we would need to process it from the highest address to the lowest,
+   in order to be agnostic to the 32 vs 64 bits issue.
+
+   returns 0 on failure, 1 if we successfully received it. */
+static int receive_bitmap(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct bm_xfer_ctx c;
+        void *buffer;
+        enum receive_bitmap_ret ret;
+        int ok = FALSE;
+
+        wait_event(mdev->misc_wait, !atomic_read(&mdev->ap_bio_cnt));
+
+        drbd_bm_lock(mdev, "receive bitmap");
+
+        /* maybe we should use some per thread scratch page,
+         * and allocate that during initial device creation? */
+        buffer   = (unsigned long *) __get_free_page(GFP_NOIO);
+        if (!buffer) {
+                dev_err(DEV, "failed to allocate one page buffer in %s\n", __func__);
+                goto out;
+        }
+
+        c = (struct bm_xfer_ctx) {
+                .bm_bits = drbd_bm_bits(mdev),
+                .bm_words = drbd_bm_words(mdev),
+        };
+
+        do {
+                if (h->command == P_BITMAP) {
+                        ret = receive_bitmap_plain(mdev, h, buffer, &c);
+                } else if (h->command == P_COMPRESSED_BITMAP) {
+                        /* MAYBE: sanity check that we speak proto >= 90,
+                         * and the feature is enabled! */
+                        struct p_compressed_bm *p;
+
+                        if (h->length > BM_PACKET_PAYLOAD_BYTES) {
+                                dev_err(DEV, "ReportCBitmap packet too large\n");
+                                goto out;
+                        }
+                        /* use the page buff */
+                        p = buffer;
+                        memcpy(p, h, sizeof(*h));
+                        if (drbd_recv(mdev, p->head.payload, h->length) != h->length)
+                                goto out;
+                        if (p->head.length <= (sizeof(*p) - sizeof(p->head))) {
+                                dev_err(DEV, "ReportCBitmap packet too small (l:%u)\n", p->head.length);
+                                return FAILED;
+                        }
+                        ret = decode_bitmap_c(mdev, p, &c);
+                } else {
+                        dev_warn(DEV, "receive_bitmap: h->command neither ReportBitMap nor ReportCBitMap (is 0x%x)", h->command);
+                        goto out;
+                }
+
+                c.packets[h->command == P_BITMAP]++;
+                c.bytes[h->command == P_BITMAP] += sizeof(struct p_header) + h->length;
+
+                if (ret != OK)
+                        break;
+
+                if (!drbd_recv_header(mdev, h))
+                        goto out;
+        } while (ret == OK);
+        if (ret == FAILED)
+                goto out;
+
+        INFO_bm_xfer_stats(mdev, "receive", &c);
+
+        if (mdev->state.conn == C_WF_BITMAP_T) {
+                ok = !drbd_send_bitmap(mdev);
+                if (!ok)
+                        goto out;
+                /* Omit CS_ORDERED with this state transition to avoid deadlocks. */
+                ok = _drbd_request_state(mdev, NS(conn, C_WF_SYNC_UUID), CS_VERBOSE);
+                D_ASSERT(ok == SS_SUCCESS);
+        } else if (mdev->state.conn != C_WF_BITMAP_S) {
+                /* admin may have requested C_DISCONNECTING,
+                 * other threads may have noticed network errors */
+                dev_info(DEV, "unexpected cstate (%s) in receive_bitmap\n",
+                    drbd_conn_str(mdev->state.conn));
+        }
+
+        ok = TRUE;
+ out:
+        drbd_bm_unlock(mdev);
+        if (ok && mdev->state.conn == C_WF_BITMAP_S)
+                drbd_start_resync(mdev, C_SYNC_SOURCE);
+        free_page((unsigned long) buffer);
+        return ok;
+}
+
+static int receive_skip(struct drbd_conf *mdev, struct p_header *h)
+{
+        /* TODO zero copy sink :) */
+        static char sink[128];
+        int size, want, r;
+
+        dev_warn(DEV, "skipping unknown optional packet type %d, l: %d!\n",
+             h->command, h->length);
+
+        size = h->length;
+        while (size > 0) {
+                want = min_t(int, size, sizeof(sink));
+                r = drbd_recv(mdev, sink, want);
+                ERR_IF(r <= 0) break;
+                size -= r;
+        }
+        return size == 0;
+}
+
+static int receive_UnplugRemote(struct drbd_conf *mdev, struct p_header *h)
+{
+        if (mdev->state.disk >= D_INCONSISTENT)
+                drbd_kick_lo(mdev);
+
+        /* Make sure we've acked all the TCP data associated
+         * with the data requests being unplugged */
+        drbd_tcp_quickack(mdev->data.socket);
+
+        return TRUE;
+}
+
+typedef int (*drbd_cmd_handler_f)(struct drbd_conf *, struct p_header *);
+
+static drbd_cmd_handler_f drbd_default_handler[] = {
+        [P_DATA]            = receive_Data,
+        [P_DATA_REPLY]      = receive_DataReply,
+        [P_RS_DATA_REPLY]   = receive_RSDataReply,
+        [P_BARRIER]         = receive_Barrier,
+        [P_BITMAP]          = receive_bitmap,
+        [P_COMPRESSED_BITMAP]    = receive_bitmap,
+        [P_UNPLUG_REMOTE]   = receive_UnplugRemote,
+        [P_DATA_REQUEST]    = receive_DataRequest,
+        [P_RS_DATA_REQUEST] = receive_DataRequest,
+        [P_SYNC_PARAM]      = receive_SyncParam,
+        [P_SYNC_PARAM89]           = receive_SyncParam,
+        [P_PROTOCOL]        = receive_protocol,
+        [P_UUIDS]           = receive_uuids,
+        [P_SIZES]           = receive_sizes,
+        [P_STATE]           = receive_state,
+        [P_STATE_CHG_REQ]   = receive_req_state,
+        [P_SYNC_UUID]       = receive_sync_uuid,
+        [P_OV_REQUEST]      = receive_DataRequest,
+        [P_OV_REPLY]        = receive_DataRequest,
+        [P_CSUM_RS_REQUEST]    = receive_DataRequest,
+        /* anything missing from this table is in
+         * the asender_tbl, see get_asender_cmd */
+        [P_MAX_CMD]         = NULL,
+};
+
+static drbd_cmd_handler_f *drbd_cmd_handler = drbd_default_handler;
+static drbd_cmd_handler_f *drbd_opt_cmd_handler;
+
+static void drbdd(struct drbd_conf *mdev)
+{
+        drbd_cmd_handler_f handler;
+        struct p_header *header = &mdev->data.rbuf.header;
+
+        while (get_t_state(&mdev->receiver) == Running) {
+                drbd_thread_current_set_cpu(mdev);
+                if (!drbd_recv_header(mdev, header))
+                        break;
+
+                if (header->command < P_MAX_CMD)
+                        handler = drbd_cmd_handler[header->command];
+                else if (P_MAY_IGNORE < header->command
+                     && header->command < P_MAX_OPT_CMD)
+                        handler = drbd_opt_cmd_handler[header->command-P_MAY_IGNORE];
+                else if (header->command > P_MAX_OPT_CMD)
+                        handler = receive_skip;
+                else
+                        handler = NULL;
+
+                if (unlikely(!handler)) {
+                        dev_err(DEV, "unknown packet type %d, l: %d!\n",
+                            header->command, header->length);
+                        drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+                        break;
+                }
+                if (unlikely(!handler(mdev, header))) {
+                        dev_err(DEV, "error receiving %s, l: %d!\n",
+                            cmdname(header->command), header->length);
+                        drbd_force_state(mdev, NS(conn, C_PROTOCOL_ERROR));
+                        break;
+                }
+
+                trace_drbd_packet(mdev, mdev->data.socket, 2, &mdev->data.rbuf,
+                                __FILE__, __LINE__);
+        }
+}
+
+static void drbd_fail_pending_reads(struct drbd_conf *mdev)
+{
+        struct hlist_head *slot;
+        struct hlist_node *pos;
+        struct hlist_node *tmp;
+        struct drbd_request *req;
+        int i;
+
+        /*
+         * Application READ requests
+         */
+        spin_lock_irq(&mdev->req_lock);
+        for (i = 0; i < APP_R_HSIZE; i++) {
+                slot = mdev->app_reads_hash+i;
+                hlist_for_each_entry_safe(req, pos, tmp, slot, colision) {
+                        /* it may (but should not any longer!)
+                         * be on the work queue; if that assert triggers,
+                         * we need to also grab the
+                         * spin_lock_irq(&mdev->data.work.q_lock);
+                         * and list_del_init here. */
+                        D_ASSERT(list_empty(&req->w.list));
+                        /* It would be nice to complete outside of spinlock.
+                         * But this is easier for now. */
+                        _req_mod(req, connection_lost_while_pending);
+                }
+        }
+        for (i = 0; i < APP_R_HSIZE; i++)
+                if (!hlist_empty(mdev->app_reads_hash+i))
+                        dev_warn(DEV, "ASSERT FAILED: app_reads_hash[%d].first: "
+                                "%p, should be NULL\n", i, mdev->app_reads_hash[i].first);
+
+        memset(mdev->app_reads_hash, 0, APP_R_HSIZE*sizeof(void *));
+        spin_unlock_irq(&mdev->req_lock);
+}
+
+void drbd_flush_workqueue(struct drbd_conf *mdev)
+{
+        struct drbd_wq_barrier barr;
+
+        barr.w.cb = w_prev_work_done;
+        init_completion(&barr.done);
+        drbd_queue_work(&mdev->data.work, &barr.w);
+        wait_for_completion(&barr.done);
+}
+
+static void drbd_disconnect(struct drbd_conf *mdev)
+{
+        enum drbd_fencing_p fp;
+        union drbd_state os, ns;
+        int rv = SS_UNKNOWN_ERROR;
+        unsigned int i;
+
+        if (mdev->state.conn == C_STANDALONE)
+                return;
+        if (mdev->state.conn >= C_WF_CONNECTION)
+                dev_err(DEV, "ASSERT FAILED cstate = %s, expected < WFConnection\n",
+                                drbd_conn_str(mdev->state.conn));
+
+        /* asender does not clean up anything. it must not interfere, either */
+        drbd_thread_stop(&mdev->asender);
+
+        mutex_lock(&mdev->data.mutex);
+        drbd_free_sock(mdev);
+        mutex_unlock(&mdev->data.mutex);
+
+        spin_lock_irq(&mdev->req_lock);
+        _drbd_wait_ee_list_empty(mdev, &mdev->active_ee);
+        _drbd_wait_ee_list_empty(mdev, &mdev->sync_ee);
+        _drbd_wait_ee_list_empty(mdev, &mdev->read_ee);
+        spin_unlock_irq(&mdev->req_lock);
+
+        /* We do not have data structures that would allow us to
+         * get the rs_pending_cnt down to 0 again.
+         *  * On C_SYNC_TARGET we do not have any data structures describing
+         *    the pending RSDataRequest's we have sent.
+         *  * On C_SYNC_SOURCE there is no data structure that tracks
+         *    the P_RS_DATA_REPLY blocks that we sent to the SyncTarget.
+         *  And no, it is not the sum of the reference counts in the
+         *  resync_LRU. The resync_LRU tracks the whole operation including
+         *  the disk-IO, while the rs_pending_cnt only tracks the blocks
+         *  on the fly. */
+        drbd_rs_cancel_all(mdev);
+        mdev->rs_total = 0;
+        mdev->rs_failed = 0;
+        atomic_set(&mdev->rs_pending_cnt, 0);
+        wake_up(&mdev->misc_wait);
+
+        /* make sure syncer is stopped and w_resume_next_sg queued */
+        del_timer_sync(&mdev->resync_timer);
+        set_bit(STOP_SYNC_TIMER, &mdev->flags);
+        resync_timer_fn((unsigned long)mdev);
+
+        /* so we can be sure that all remote or resync reads
+         * made it at least to net_ee */
+        wait_event(mdev->misc_wait, !atomic_read(&mdev->local_cnt));
+
+        /* wait for all w_e_end_data_req, w_e_end_rsdata_req, w_send_barrier,
+         * w_make_resync_request etc. which may still be on the worker queue
+         * to be "canceled" */
+        drbd_flush_workqueue(mdev);
+
+        /* This also does reclaim_net_ee().  If we do this too early, we might
+         * miss some resync ee and pages.*/
+        drbd_process_done_ee(mdev);
+
+        kfree(mdev->p_uuid);
+        mdev->p_uuid = NULL;
+
+        if (!mdev->state.susp)
+                tl_clear(mdev);
+
+        drbd_fail_pending_reads(mdev);
+
+        dev_info(DEV, "Connection closed\n");
+
+        drbd_md_sync(mdev);
+
+        fp = FP_DONT_CARE;
+        if (get_ldev(mdev)) {
+                fp = mdev->ldev->dc.fencing;
+                put_ldev(mdev);
+        }
+
+        if (mdev->state.role == R_PRIMARY) {
+                if (fp >= FP_RESOURCE && mdev->state.pdsk >= D_UNKNOWN) {
+                        enum drbd_disk_state nps = drbd_try_outdate_peer(mdev);
+                        drbd_request_state(mdev, NS(pdsk, nps));
+                }
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        os = mdev->state;
+        if (os.conn >= C_UNCONNECTED) {
+                /* Do not restart in case we are C_DISCONNECTING */
+                ns = os;
+                ns.conn = C_UNCONNECTED;
+                rv = _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+        }
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (os.conn == C_DISCONNECTING) {
+                struct hlist_head *h;
+                wait_event(mdev->misc_wait, atomic_read(&mdev->net_cnt) == 0);
+
+                /* we must not free the tl_hash
+                 * while application io is still on the fly */
+                wait_event(mdev->misc_wait, atomic_read(&mdev->ap_bio_cnt) == 0);
+
+                spin_lock_irq(&mdev->req_lock);
+                /* paranoia code */
+                for (h = mdev->ee_hash; h < mdev->ee_hash + mdev->ee_hash_s; h++)
+                        if (h->first)
+                                dev_err(DEV, "ASSERT FAILED ee_hash[%u].first == %p, expected NULL\n",
+                                                (int)(h - mdev->ee_hash), h->first);
+                kfree(mdev->ee_hash);
+                mdev->ee_hash = NULL;
+                mdev->ee_hash_s = 0;
+
+                /* paranoia code */
+                for (h = mdev->tl_hash; h < mdev->tl_hash + mdev->tl_hash_s; h++)
+                        if (h->first)
+                                dev_err(DEV, "ASSERT FAILED tl_hash[%u] == %p, expected NULL\n",
+                                                (int)(h - mdev->tl_hash), h->first);
+                kfree(mdev->tl_hash);
+                mdev->tl_hash = NULL;
+                mdev->tl_hash_s = 0;
+                spin_unlock_irq(&mdev->req_lock);
+
+                crypto_free_hash(mdev->cram_hmac_tfm);
+                mdev->cram_hmac_tfm = NULL;
+
+                kfree(mdev->net_conf);
+                mdev->net_conf = NULL;
+                drbd_request_state(mdev, NS(conn, C_STANDALONE));
+        }
+
+        /* tcp_close and release of sendpage pages can be deferred.  I don't
+         * want to use SO_LINGER, because apparently it can be deferred for
+         * more than 20 seconds (longest time I checked).
+         *
+         * Actually we don't care for exactly when the network stack does its
+         * put_page(), but release our reference on these pages right here.
+         */
+        i = drbd_release_ee(mdev, &mdev->net_ee);
+        if (i)
+                dev_info(DEV, "net_ee not empty, killed %u entries\n", i);
+        i = atomic_read(&mdev->pp_in_use);
+        if (i)
+                dev_info(DEV, "pp_in_use = %u, expected 0\n", i);
+
+        D_ASSERT(list_empty(&mdev->read_ee));
+        D_ASSERT(list_empty(&mdev->active_ee));
+        D_ASSERT(list_empty(&mdev->sync_ee));
+        D_ASSERT(list_empty(&mdev->done_ee));
+
+        /* ok, no more ee's on the fly, it is safe to reset the epoch_size */
+        atomic_set(&mdev->current_epoch->epoch_size, 0);
+        D_ASSERT(list_empty(&mdev->current_epoch->list));
+}
+
+/*
+ * We support PRO_VERSION_MIN to PRO_VERSION_MAX. The protocol version
+ * we can agree on is stored in agreed_pro_version.
+ *
+ * feature flags and the reserved array should be enough room for future
+ * enhancements of the handshake protocol, and possible plugins...
+ *
+ * for now, they are expected to be zero, but ignored.
+ */
+static int drbd_send_handshake(struct drbd_conf *mdev)
+{
+        /* ASSERT current == mdev->receiver ... */
+        struct p_handshake *p = &mdev->data.sbuf.handshake;
+        int ok;
+
+        if (mutex_lock_interruptible(&mdev->data.mutex)) {
+                dev_err(DEV, "interrupted during initial handshake\n");
+                return 0; /* interrupted. not ok. */
+        }
+
+        if (mdev->data.socket == NULL) {
+                mutex_unlock(&mdev->data.mutex);
+                return 0;
+        }
+
+        memset(p, 0, sizeof(*p));
+        p->protocol_min = cpu_to_be32(PRO_VERSION_MIN);
+        p->protocol_max = cpu_to_be32(PRO_VERSION_MAX);
+        ok = _drbd_send_cmd( mdev, mdev->data.socket, P_HAND_SHAKE,
+                             (struct p_header *)p, sizeof(*p), 0 );
+        mutex_unlock(&mdev->data.mutex);
+        return ok;
+}
+
+/*
+ * return values:
+ *   1 yes, we have a valid connection
+ *   0 oops, did not work out, please try again
+ *  -1 peer talks different language,
+ *     no point in trying again, please go standalone.
+ */
+static int drbd_do_handshake(struct drbd_conf *mdev)
+{
+        /* ASSERT current == mdev->receiver ... */
+        struct p_handshake *p = &mdev->data.rbuf.handshake;
+        const int expect = sizeof(struct p_handshake)
+                          -sizeof(struct p_header);
+        int rv;
+
+        rv = drbd_send_handshake(mdev);
+        if (!rv)
+                return 0;
+
+        rv = drbd_recv_header(mdev, &p->head);
+        if (!rv)
+                return 0;
+
+        if (p->head.command != P_HAND_SHAKE) {
+                dev_err(DEV, "expected HandShake packet, received: %s (0x%04x)\n",
+                     cmdname(p->head.command), p->head.command);
+                return -1;
+        }
+
+        if (p->head.length != expect) {
+                dev_err(DEV, "expected HandShake length: %u, received: %u\n",
+                     expect, p->head.length);
+                return -1;
+        }
+
+        rv = drbd_recv(mdev, &p->head.payload, expect);
+
+        if (rv != expect) {
+                dev_err(DEV, "short read receiving handshake packet: l=%u\n", rv);
+                return 0;
+        }
+
+        trace_drbd_packet(mdev, mdev->data.socket, 2, &mdev->data.rbuf,
+                        __FILE__, __LINE__);
+
+        p->protocol_min = be32_to_cpu(p->protocol_min);
+        p->protocol_max = be32_to_cpu(p->protocol_max);
+        if (p->protocol_max == 0)
+                p->protocol_max = p->protocol_min;
+
+        if (PRO_VERSION_MAX < p->protocol_min ||
+            PRO_VERSION_MIN > p->protocol_max)
+                goto incompat;
+
+        mdev->agreed_pro_version = min_t(int, PRO_VERSION_MAX, p->protocol_max);
+
+        dev_info(DEV, "Handshake successful: "
+             "Agreed network protocol version %d\n", mdev->agreed_pro_version);
+
+        return 1;
+
+ incompat:
+        dev_err(DEV, "incompatible DRBD dialects: "
+            "I support %d-%d, peer supports %d-%d\n",
+            PRO_VERSION_MIN, PRO_VERSION_MAX,
+            p->protocol_min, p->protocol_max);
+        return -1;
+}
+
+#if !defined(CONFIG_CRYPTO_HMAC) && !defined(CONFIG_CRYPTO_HMAC_MODULE)
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+        dev_err(DEV, "This kernel was build without CONFIG_CRYPTO_HMAC.\n");
+        dev_err(DEV, "You need to disable 'cram-hmac-alg' in drbd.conf.\n");
+        return 0;
+}
+#else
+#define CHALLENGE_LEN 64
+static int drbd_do_auth(struct drbd_conf *mdev)
+{
+        char my_challenge[CHALLENGE_LEN];  /* 64 Bytes... */
+        struct scatterlist sg;
+        char *response = NULL;
+        char *right_response = NULL;
+        char *peers_ch = NULL;
+        struct p_header p;
+        unsigned int key_len = strlen(mdev->net_conf->shared_secret);
+        unsigned int resp_size;
+        struct hash_desc desc;
+        int rv;
+
+        desc.tfm = mdev->cram_hmac_tfm;
+        desc.flags = 0;
+
+        rv = crypto_hash_setkey(mdev->cram_hmac_tfm,
+                                (u8 *)mdev->net_conf->shared_secret, key_len);
+        if (rv) {
+                dev_err(DEV, "crypto_hash_setkey() failed with %d\n", rv);
+                rv = 0;
+                goto fail;
+        }
+
+        get_random_bytes(my_challenge, CHALLENGE_LEN);
+
+        rv = drbd_send_cmd2(mdev, P_AUTH_CHALLENGE, my_challenge, CHALLENGE_LEN);
+        if (!rv)
+                goto fail;
+
+        rv = drbd_recv_header(mdev, &p);
+        if (!rv)
+                goto fail;
+
+        if (p.command != P_AUTH_CHALLENGE) {
+                dev_err(DEV, "expected AuthChallenge packet, received: %s (0x%04x)\n",
+                    cmdname(p.command), p.command);
+                rv = 0;
+                goto fail;
+        }
+
+        if (p.length > CHALLENGE_LEN*2) {
+                dev_err(DEV, "expected AuthChallenge payload too big.\n");
+                rv = 0;
+                goto fail;
+        }
+
+        peers_ch = kmalloc(p.length, GFP_NOIO);
+        if (peers_ch == NULL) {
+                dev_err(DEV, "kmalloc of peers_ch failed\n");
+                rv = 0;
+                goto fail;
+        }
+
+        rv = drbd_recv(mdev, peers_ch, p.length);
+
+        if (rv != p.length) {
+                dev_err(DEV, "short read AuthChallenge: l=%u\n", rv);
+                rv = 0;
+                goto fail;
+        }
+
+        resp_size = crypto_hash_digestsize(mdev->cram_hmac_tfm);
+        response = kmalloc(resp_size, GFP_NOIO);
+        if (response == NULL) {
+                dev_err(DEV, "kmalloc of response failed\n");
+                rv = 0;
+                goto fail;
+        }
+
+        sg_init_table(&sg, 1);
+        sg_set_buf(&sg, peers_ch, p.length);
+
+        rv = crypto_hash_digest(&desc, &sg, sg.length, response);
+        if (rv) {
+                dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+                rv = 0;
+                goto fail;
+        }
+
+        rv = drbd_send_cmd2(mdev, P_AUTH_RESPONSE, response, resp_size);
+        if (!rv)
+                goto fail;
+
+        rv = drbd_recv_header(mdev, &p);
+        if (!rv)
+                goto fail;
+
+        if (p.command != P_AUTH_RESPONSE) {
+                dev_err(DEV, "expected AuthResponse packet, received: %s (0x%04x)\n",
+                    cmdname(p.command), p.command);
+                rv = 0;
+                goto fail;
+        }
+
+        if (p.length != resp_size) {
+                dev_err(DEV, "expected AuthResponse payload of wrong size\n");
+                rv = 0;
+                goto fail;
+        }
+
+        rv = drbd_recv(mdev, response , resp_size);
+
+        if (rv != resp_size) {
+                dev_err(DEV, "short read receiving AuthResponse: l=%u\n", rv);
+                rv = 0;
+                goto fail;
+        }
+
+        right_response = kmalloc(resp_size, GFP_NOIO);
+        if (response == NULL) {
+                dev_err(DEV, "kmalloc of right_response failed\n");
+                rv = 0;
+                goto fail;
+        }
+
+        sg_set_buf(&sg, my_challenge, CHALLENGE_LEN);
+
+        rv = crypto_hash_digest(&desc, &sg, sg.length, right_response);
+        if (rv) {
+                dev_err(DEV, "crypto_hash_digest() failed with %d\n", rv);
+                rv = 0;
+                goto fail;
+        }
+
+        rv = !memcmp(response, right_response, resp_size);
+
+        if (rv)
+                dev_info(DEV, "Peer authenticated using %d bytes of '%s' HMAC\n",
+                     resp_size, mdev->net_conf->cram_hmac_alg);
+
+ fail:
+        kfree(peers_ch);
+        kfree(response);
+        kfree(right_response);
+
+        return rv;
+}
+#endif
+
+int drbdd_init(struct drbd_thread *thi)
+{
+        struct drbd_conf *mdev = thi->mdev;
+        unsigned int minor = mdev_to_minor(mdev);
+        int h;
+
+        sprintf(current->comm, "drbd%d_receiver", minor);
+
+        dev_info(DEV, "receiver (re)started\n");
+
+        do {
+                h = drbd_connect(mdev);
+                if (h == 0) {
+                        drbd_disconnect(mdev);
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(HZ);
+                }
+                if (h == -1) {
+                        dev_warn(DEV, "Discarding network configuration.\n");
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                }
+        } while (h == 0);
+
+        if (h > 0) {
+                if (get_net_conf(mdev)) {
+                        drbdd(mdev);
+                        put_net_conf(mdev);
+                }
+        }
+
+        drbd_disconnect(mdev);
+
+        dev_info(DEV, "receiver terminated\n");
+        return 0;
+}
+
+/* ********* acknowledge sender ******** */
+
+static int got_RqSReply(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_req_state_reply *p = (struct p_req_state_reply *)h;
+
+        int retcode = be32_to_cpu(p->retcode);
+
+        if (retcode >= SS_SUCCESS) {
+                set_bit(CL_ST_CHG_SUCCESS, &mdev->flags);
+        } else {
+                set_bit(CL_ST_CHG_FAIL, &mdev->flags);
+                dev_err(DEV, "Requested state change failed by peer: %s (%d)\n",
+                    drbd_set_st_err_str(retcode), retcode);
+        }
+        wake_up(&mdev->state_wait);
+
+        return TRUE;
+}
+
+static int got_Ping(struct drbd_conf *mdev, struct p_header *h)
+{
+        return drbd_send_ping_ack(mdev);
+
+}
+
+static int got_PingAck(struct drbd_conf *mdev, struct p_header *h)
+{
+        /* restore idle timeout */
+        mdev->meta.socket->sk->sk_rcvtimeo = mdev->net_conf->ping_int*HZ;
+
+        return TRUE;
+}
+
+static int got_IsInSync(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_block_ack *p = (struct p_block_ack *)h;
+        sector_t sector = be64_to_cpu(p->sector);
+        int blksize = be32_to_cpu(p->blksize);
+
+        D_ASSERT(mdev->agreed_pro_version >= 89);
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+        drbd_rs_complete_io(mdev, sector);
+        drbd_set_in_sync(mdev, sector, blksize);
+        /* rs_same_csums is supposed to count in units of BM_BLOCK_SIZE */
+        mdev->rs_same_csum += (blksize >> BM_BLOCK_SHIFT);
+        dec_rs_pending(mdev);
+
+        return TRUE;
+}
+
+/* when we receive the ACK for a write request,
+ * verify that we actually know about it */
+static struct drbd_request *_ack_id_to_req(struct drbd_conf *mdev,
+        u64 id, sector_t sector)
+{
+        struct hlist_head *slot = tl_hash_slot(mdev, sector);
+        struct hlist_node *n;
+        struct drbd_request *req;
+
+        hlist_for_each_entry(req, n, slot, colision) {
+                if ((unsigned long)req == (unsigned long)id) {
+                        if (req->sector != sector) {
+                                dev_err(DEV, "_ack_id_to_req: found req %p but it has "
+                                    "wrong sector (%llus versus %llus)\n", req,
+                                    (unsigned long long)req->sector,
+                                    (unsigned long long)sector);
+                                break;
+                        }
+                        return req;
+                }
+        }
+        dev_err(DEV, "_ack_id_to_req: failed to find req %p, sector %llus in list\n",
+                (void *)(unsigned long)id, (unsigned long long)sector);
+        return NULL;
+}
+
+typedef struct drbd_request *(req_validator_fn)
+        (struct drbd_conf *mdev, u64 id, sector_t sector);
+
+static int validate_req_change_req_state(struct drbd_conf *mdev,
+        u64 id, sector_t sector, req_validator_fn validator,
+        const char *func, enum drbd_req_event what)
+{
+        struct drbd_request *req;
+        struct bio_and_error m;
+
+        spin_lock_irq(&mdev->req_lock);
+        req = validator(mdev, id, sector);
+        if (unlikely(!req)) {
+                spin_unlock_irq(&mdev->req_lock);
+                dev_err(DEV, "%s: got a corrupt block_id/sector pair\n", func);
+                return FALSE;
+        }
+        __req_mod(req, what, &m);
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+        return TRUE;
+}
+
+static int got_BlockAck(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_block_ack *p = (struct p_block_ack *)h;
+        sector_t sector = be64_to_cpu(p->sector);
+        int blksize = be32_to_cpu(p->blksize);
+        enum drbd_req_event what;
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+        if (is_syncer_block_id(p->block_id)) {
+                drbd_set_in_sync(mdev, sector, blksize);
+                dec_rs_pending(mdev);
+                return TRUE;
+        }
+        switch (be16_to_cpu(h->command)) {
+        case P_RS_WRITE_ACK:
+                D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+                what = write_acked_by_peer_and_sis;
+                break;
+        case P_WRITE_ACK:
+                D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+                what = write_acked_by_peer;
+                break;
+        case P_RECV_ACK:
+                D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_B);
+                what = recv_acked_by_peer;
+                break;
+        case P_DISCARD_ACK:
+                D_ASSERT(mdev->net_conf->wire_protocol == DRBD_PROT_C);
+                what = conflict_discarded_by_peer;
+                break;
+        default:
+                D_ASSERT(0);
+                return FALSE;
+        }
+
+        return validate_req_change_req_state(mdev, p->block_id, sector,
+                _ack_id_to_req, __func__ , what);
+}
+
+static int got_NegAck(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_block_ack *p = (struct p_block_ack *)h;
+        sector_t sector = be64_to_cpu(p->sector);
+
+        if (__ratelimit(&drbd_ratelimit_state))
+                dev_warn(DEV, "Got NegAck packet. Peer is in troubles?\n");
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+        if (is_syncer_block_id(p->block_id)) {
+                int size = be32_to_cpu(p->blksize);
+                dec_rs_pending(mdev);
+                drbd_rs_failed_io(mdev, sector, size);
+                return TRUE;
+        }
+        return validate_req_change_req_state(mdev, p->block_id, sector,
+                _ack_id_to_req, __func__ , neg_acked);
+}
+
+static int got_NegDReply(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_block_ack *p = (struct p_block_ack *)h;
+        sector_t sector = be64_to_cpu(p->sector);
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+        dev_err(DEV, "Got NegDReply; Sector %llus, len %u; Fail original request.\n",
+            (unsigned long long)sector, be32_to_cpu(p->blksize));
+
+        return validate_req_change_req_state(mdev, p->block_id, sector,
+                _ar_id_to_req, __func__ , neg_acked);
+}
+
+static int got_NegRSDReply(struct drbd_conf *mdev, struct p_header *h)
+{
+        sector_t sector;
+        int size;
+        struct p_block_ack *p = (struct p_block_ack *)h;
+
+        sector = be64_to_cpu(p->sector);
+        size = be32_to_cpu(p->blksize);
+        D_ASSERT(p->block_id == ID_SYNCER);
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+        dec_rs_pending(mdev);
+
+        if (get_ldev_if_state(mdev, D_FAILED)) {
+                drbd_rs_complete_io(mdev, sector);
+                drbd_rs_failed_io(mdev, sector, size);
+                put_ldev(mdev);
+        }
+
+        return TRUE;
+}
+
+static int got_BarrierAck(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_barrier_ack *p = (struct p_barrier_ack *)h;
+
+        tl_release(mdev, p->barrier, be32_to_cpu(p->set_size));
+
+        return TRUE;
+}
+
+static int got_OVResult(struct drbd_conf *mdev, struct p_header *h)
+{
+        struct p_block_ack *p = (struct p_block_ack *)h;
+        struct drbd_work *w;
+        sector_t sector;
+        int size;
+
+        sector = be64_to_cpu(p->sector);
+        size = be32_to_cpu(p->blksize);
+
+        update_peer_seq(mdev, be32_to_cpu(p->seq_num));
+
+        if (be64_to_cpu(p->block_id) == ID_OUT_OF_SYNC)
+                drbd_ov_oos_found(mdev, sector, size);
+        else
+                ov_oos_print(mdev);
+
+        drbd_rs_complete_io(mdev, sector);
+        dec_rs_pending(mdev);
+
+        if (--mdev->ov_left == 0) {
+                w = kmalloc(sizeof(*w), GFP_NOIO);
+                if (w) {
+                        w->cb = w_ov_finished;
+                        drbd_queue_work_front(&mdev->data.work, w);
+                } else {
+                        dev_err(DEV, "kmalloc(w) failed.");
+                        ov_oos_print(mdev);
+                        drbd_resync_finished(mdev);
+                }
+        }
+        return TRUE;
+}
+
+struct asender_cmd {
+        size_t pkt_size;
+        int (*process)(struct drbd_conf *mdev, struct p_header *h);
+};
+
+static struct asender_cmd *get_asender_cmd(int cmd)
+{
+        static struct asender_cmd asender_tbl[] = {
+                /* anything missing from this table is in
+                 * the drbd_cmd_handler (drbd_default_handler) table,
+                 * see the beginning of drbdd() */
+        [P_PING]            = { sizeof(struct p_header), got_Ping },
+        [P_PING_ACK]        = { sizeof(struct p_header), got_PingAck },
+        [P_RECV_ACK]        = { sizeof(struct p_block_ack), got_BlockAck },
+        [P_WRITE_ACK]       = { sizeof(struct p_block_ack), got_BlockAck },
+        [P_RS_WRITE_ACK]    = { sizeof(struct p_block_ack), got_BlockAck },
+        [P_DISCARD_ACK]     = { sizeof(struct p_block_ack), got_BlockAck },
+        [P_NEG_ACK]         = { sizeof(struct p_block_ack), got_NegAck },
+        [P_NEG_DREPLY]      = { sizeof(struct p_block_ack), got_NegDReply },
+        [P_NEG_RS_DREPLY]   = { sizeof(struct p_block_ack), got_NegRSDReply},
+        [P_OV_RESULT]       = { sizeof(struct p_block_ack), got_OVResult },
+        [P_BARRIER_ACK]     = { sizeof(struct p_barrier_ack), got_BarrierAck },
+        [P_STATE_CHG_REPLY] = { sizeof(struct p_req_state_reply), got_RqSReply },
+        [P_RS_IS_IN_SYNC]   = { sizeof(struct p_block_ack), got_IsInSync },
+        [P_MAX_CMD]         = { 0, NULL },
+        };
+        if (cmd > P_MAX_CMD || asender_tbl[cmd].process == NULL)
+                return NULL;
+        return &asender_tbl[cmd];
+}
+
+int drbd_asender(struct drbd_thread *thi)
+{
+        struct drbd_conf *mdev = thi->mdev;
+        struct p_header *h = &mdev->meta.rbuf.header;
+        struct asender_cmd *cmd = NULL;
+
+        int rv, len;
+        void *buf    = h;
+        int received = 0;
+        int expect   = sizeof(struct p_header);
+        int empty;
+
+        sprintf(current->comm, "drbd%d_asender", mdev_to_minor(mdev));
+
+        current->policy = SCHED_RR;  /* Make this a realtime task! */
+        current->rt_priority = 2;    /* more important than all other tasks */
+
+        while (get_t_state(thi) == Running) {
+                drbd_thread_current_set_cpu(mdev);
+                if (test_and_clear_bit(SEND_PING, &mdev->flags)) {
+                        ERR_IF(!drbd_send_ping(mdev)) goto reconnect;
+                        mdev->meta.socket->sk->sk_rcvtimeo =
+                                mdev->net_conf->ping_timeo*HZ/10;
+                }
+
+                /* conditionally cork;
+                 * it may hurt latency if we cork without much to send */
+                if (!mdev->net_conf->no_cork &&
+                        3 < atomic_read(&mdev->unacked_cnt))
+                        drbd_tcp_cork(mdev->meta.socket);
+                while (1) {
+                        clear_bit(SIGNAL_ASENDER, &mdev->flags);
+                        flush_signals(current);
+                        if (!drbd_process_done_ee(mdev)) {
+                                dev_err(DEV, "process_done_ee() = NOT_OK\n");
+                                goto reconnect;
+                        }
+                        /* to avoid race with newly queued ACKs */
+                        set_bit(SIGNAL_ASENDER, &mdev->flags);
+                        spin_lock_irq(&mdev->req_lock);
+                        empty = list_empty(&mdev->done_ee);
+                        spin_unlock_irq(&mdev->req_lock);
+                        /* new ack may have been queued right here,
+                         * but then there is also a signal pending,
+                         * and we start over... */
+                        if (empty)
+                                break;
+                }
+                /* but unconditionally uncork unless disabled */
+                if (!mdev->net_conf->no_cork)
+                        drbd_tcp_uncork(mdev->meta.socket);
+
+                /* short circuit, recv_msg would return EINTR anyways. */
+                if (signal_pending(current))
+                        continue;
+
+                rv = drbd_recv_short(mdev, mdev->meta.socket,
+                                     buf, expect-received, 0);
+                clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+                flush_signals(current);
+
+                /* Note:
+                 * -EINTR        (on meta) we got a signal
+                 * -EAGAIN       (on meta) rcvtimeo expired
+                 * -ECONNRESET   other side closed the connection
+                 * -ERESTARTSYS  (on data) we got a signal
+                 * rv <  0       other than above: unexpected error!
+                 * rv == expected: full header or command
+                 * rv <  expected: "woken" by signal during receive
+                 * rv == 0       : "connection shut down by peer"
+                 */
+                if (likely(rv > 0)) {
+                        received += rv;
+                        buf      += rv;
+                } else if (rv == 0) {
+                        dev_err(DEV, "meta connection shut down by peer.\n");
+                        goto reconnect;
+                } else if (rv == -EAGAIN) {
+                        if (mdev->meta.socket->sk->sk_rcvtimeo ==
+                            mdev->net_conf->ping_timeo*HZ/10) {
+                                dev_err(DEV, "PingAck did not arrive in time.\n");
+                                goto reconnect;
+                        }
+                        set_bit(SEND_PING, &mdev->flags);
+                        continue;
+                } else if (rv == -EINTR) {
+                        continue;
+                } else {
+                        dev_err(DEV, "sock_recvmsg returned %d\n", rv);
+                        goto reconnect;
+                }
+
+                if (received == expect && cmd == NULL) {
+                        if (unlikely(h->magic != BE_DRBD_MAGIC)) {
+                                dev_err(DEV, "magic?? on meta m: 0x%lx c: %d l: %d\n",
+                                    (long)be32_to_cpu(h->magic),
+                                    h->command, h->length);
+                                goto reconnect;
+                        }
+                        cmd = get_asender_cmd(be16_to_cpu(h->command));
+                        len = be16_to_cpu(h->length);
+                        if (unlikely(cmd == NULL)) {
+                                dev_err(DEV, "unknown command?? on meta m: 0x%lx c: %d l: %d\n",
+                                    (long)be32_to_cpu(h->magic),
+                                    h->command, h->length);
+                                goto disconnect;
+                        }
+                        expect = cmd->pkt_size;
+                        ERR_IF(len != expect-sizeof(struct p_header)) {
+                                trace_drbd_packet(mdev, mdev->meta.socket, 1, (void *)h, __FILE__, __LINE__);
+                                goto reconnect;
+                        }
+                }
+                if (received == expect) {
+                        D_ASSERT(cmd != NULL);
+                        trace_drbd_packet(mdev, mdev->meta.socket, 1, (void *)h, __FILE__, __LINE__);
+                        if (!cmd->process(mdev, h))
+                                goto reconnect;
+
+                        buf      = h;
+                        received = 0;
+                        expect   = sizeof(struct p_header);
+                        cmd      = NULL;
+                }
+        }
+
+        if (0) {
+reconnect:
+                drbd_force_state(mdev, NS(conn, C_NETWORK_FAILURE));
+        }
+        if (0) {
+disconnect:
+                drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+        }
+        clear_bit(SIGNAL_ASENDER, &mdev->flags);
+
+        D_ASSERT(mdev->state.conn < C_CONNECTED);
+        dev_info(DEV, "asender terminated\n");
+
+        return 0;
+}
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
new file mode 100644
index 000000000000..0656cf1edd57
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.c
@@ -0,0 +1,1132 @@
+/*
+   drbd_req.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include "drbd_req.h"
+
+
+/* Update disk stats at start of I/O request */
+static void _drbd_start_io_acct(struct drbd_conf *mdev, struct drbd_request *req, struct bio *bio)
+{
+        const int rw = bio_data_dir(bio);
+        int cpu;
+        cpu = part_stat_lock();
+        part_stat_inc(cpu, &mdev->vdisk->part0, ios[rw]);
+        part_stat_add(cpu, &mdev->vdisk->part0, sectors[rw], bio_sectors(bio));
+        part_stat_unlock();
+        mdev->vdisk->part0.in_flight[rw]++;
+}
+
+/* Update disk stats when completing request upwards */
+static void _drbd_end_io_acct(struct drbd_conf *mdev, struct drbd_request *req)
+{
+        int rw = bio_data_dir(req->master_bio);
+        unsigned long duration = jiffies - req->start_time;
+        int cpu;
+        cpu = part_stat_lock();
+        part_stat_add(cpu, &mdev->vdisk->part0, ticks[rw], duration);
+        part_round_stats(cpu, &mdev->vdisk->part0);
+        part_stat_unlock();
+        mdev->vdisk->part0.in_flight[rw]--;
+}
+
+static void _req_is_done(struct drbd_conf *mdev, struct drbd_request *req, const int rw)
+{
+        const unsigned long s = req->rq_state;
+        /* if it was a write, we may have to set the corresponding
+         * bit(s) out-of-sync first. If it had a local part, we need to
+         * release the reference to the activity log. */
+        if (rw == WRITE) {
+                /* remove it from the transfer log.
+                 * well, only if it had been there in the first
+                 * place... if it had not (local only or conflicting
+                 * and never sent), it should still be "empty" as
+                 * initialized in drbd_req_new(), so we can list_del() it
+                 * here unconditionally */
+                list_del(&req->tl_requests);
+                /* Set out-of-sync unless both OK flags are set
+                 * (local only or remote failed).
+                 * Other places where we set out-of-sync:
+                 * READ with local io-error */
+                if (!(s & RQ_NET_OK) || !(s & RQ_LOCAL_OK))
+                        drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+                if ((s & RQ_NET_OK) && (s & RQ_LOCAL_OK) && (s & RQ_NET_SIS))
+                        drbd_set_in_sync(mdev, req->sector, req->size);
+
+                /* one might be tempted to move the drbd_al_complete_io
+                 * to the local io completion callback drbd_endio_pri.
+                 * but, if this was a mirror write, we may only
+                 * drbd_al_complete_io after this is RQ_NET_DONE,
+                 * otherwise the extent could be dropped from the al
+                 * before it has actually been written on the peer.
+                 * if we crash before our peer knows about the request,
+                 * but after the extent has been dropped from the al,
+                 * we would forget to resync the corresponding extent.
+                 */
+                if (s & RQ_LOCAL_MASK) {
+                        if (get_ldev_if_state(mdev, D_FAILED)) {
+                                drbd_al_complete_io(mdev, req->sector);
+                                put_ldev(mdev);
+                        } else if (__ratelimit(&drbd_ratelimit_state)) {
+                                dev_warn(DEV, "Should have called drbd_al_complete_io(, %llu), "
+                                     "but my Disk seems to have failed :(\n",
+                                     (unsigned long long) req->sector);
+                        }
+                }
+        }
+
+        /* if it was a local io error, we want to notify our
+         * peer about that, and see if we need to
+         * detach the disk and stuff.
+         * to avoid allocating some special work
+         * struct, reuse the request. */
+
+        /* THINK
+         * why do we do this not when we detect the error,
+         * but delay it until it is "done", i.e. possibly
+         * until the next barrier ack? */
+
+        if (rw == WRITE &&
+            ((s & RQ_LOCAL_MASK) && !(s & RQ_LOCAL_OK))) {
+                if (!(req->w.list.next == LIST_POISON1 ||
+                      list_empty(&req->w.list))) {
+                        /* DEBUG ASSERT only; if this triggers, we
+                         * probably corrupt the worker list here */
+                        dev_err(DEV, "req->w.list.next = %p\n", req->w.list.next);
+                        dev_err(DEV, "req->w.list.prev = %p\n", req->w.list.prev);
+                }
+                req->w.cb = w_io_error;
+                drbd_queue_work(&mdev->data.work, &req->w);
+                /* drbd_req_free() is done in w_io_error */
+        } else {
+                drbd_req_free(req);
+        }
+}
+
+static void queue_barrier(struct drbd_conf *mdev)
+{
+        struct drbd_tl_epoch *b;
+
+        /* We are within the req_lock. Once we queued the barrier for sending,
+         * we set the CREATE_BARRIER bit. It is cleared as soon as a new
+         * barrier/epoch object is added. This is the only place this bit is
+         * set. It indicates that the barrier for this epoch is already queued,
+         * and no new epoch has been created yet. */
+        if (test_bit(CREATE_BARRIER, &mdev->flags))
+                return;
+
+        b = mdev->newest_tle;
+        b->w.cb = w_send_barrier;
+        /* inc_ap_pending done here, so we won't
+         * get imbalanced on connection loss.
+         * dec_ap_pending will be done in got_BarrierAck
+         * or (on connection loss) in tl_clear.  */
+        inc_ap_pending(mdev);
+        drbd_queue_work(&mdev->data.work, &b->w);
+        set_bit(CREATE_BARRIER, &mdev->flags);
+}
+
+static void _about_to_complete_local_write(struct drbd_conf *mdev,
+        struct drbd_request *req)
+{
+        const unsigned long s = req->rq_state;
+        struct drbd_request *i;
+        struct drbd_epoch_entry *e;
+        struct hlist_node *n;
+        struct hlist_head *slot;
+
+        /* before we can signal completion to the upper layers,
+         * we may need to close the current epoch */
+        if (mdev->state.conn >= C_CONNECTED &&
+            req->epoch == mdev->newest_tle->br_number)
+                queue_barrier(mdev);
+
+        /* we need to do the conflict detection stuff,
+         * if we have the ee_hash (two_primaries) and
+         * this has been on the network */
+        if ((s & RQ_NET_DONE) && mdev->ee_hash != NULL) {
+                const sector_t sector = req->sector;
+                const int size = req->size;
+
+                /* ASSERT:
+                 * there must be no conflicting requests, since
+                 * they must have been failed on the spot */
+#define OVERLAPS overlaps(sector, size, i->sector, i->size)
+                slot = tl_hash_slot(mdev, sector);
+                hlist_for_each_entry(i, n, slot, colision) {
+                        if (OVERLAPS) {
+                                dev_alert(DEV, "LOGIC BUG: completed: %p %llus +%u; "
+                                      "other: %p %llus +%u\n",
+                                      req, (unsigned long long)sector, size,
+                                      i, (unsigned long long)i->sector, i->size);
+                        }
+                }
+
+                /* maybe "wake" those conflicting epoch entries
+                 * that wait for this request to finish.
+                 *
+                 * currently, there can be only _one_ such ee
+                 * (well, or some more, which would be pending
+                 * P_DISCARD_ACK not yet sent by the asender...),
+                 * since we block the receiver thread upon the
+                 * first conflict detection, which will wait on
+                 * misc_wait.  maybe we want to assert that?
+                 *
+                 * anyways, if we found one,
+                 * we just have to do a wake_up.  */
+#undef OVERLAPS
+#define OVERLAPS overlaps(sector, size, e->sector, e->size)
+                slot = ee_hash_slot(mdev, req->sector);
+                hlist_for_each_entry(e, n, slot, colision) {
+                        if (OVERLAPS) {
+                                wake_up(&mdev->misc_wait);
+                                break;
+                        }
+                }
+        }
+#undef OVERLAPS
+}
+
+void complete_master_bio(struct drbd_conf *mdev,
+                struct bio_and_error *m)
+{
+        trace_drbd_bio(mdev, "Rq", m->bio, 1, NULL);
+        bio_endio(m->bio, m->error);
+        dec_ap_bio(mdev);
+}
+
+/* Helper for __req_mod().
+ * Set m->bio to the master bio, if it is fit to be completed,
+ * or leave it alone (it is initialized to NULL in __req_mod),
+ * if it has already been completed, or cannot be completed yet.
+ * If m->bio is set, the error status to be returned is placed in m->error.
+ */
+void _req_may_be_done(struct drbd_request *req, struct bio_and_error *m)
+{
+        const unsigned long s = req->rq_state;
+        struct drbd_conf *mdev = req->mdev;
+        /* only WRITES may end up here without a master bio (on barrier ack) */
+        int rw = req->master_bio ? bio_data_dir(req->master_bio) : WRITE;
+
+        trace_drbd_req(req, nothing, "_req_may_be_done");
+
+        /* we must not complete the master bio, while it is
+         *      still being processed by _drbd_send_zc_bio (drbd_send_dblock)
+         *      not yet acknowledged by the peer
+         *      not yet completed by the local io subsystem
+         * these flags may get cleared in any order by
+         *      the worker,
+         *      the receiver,
+         *      the bio_endio completion callbacks.
+         */
+        if (s & RQ_NET_QUEUED)
+                return;
+        if (s & RQ_NET_PENDING)
+                return;
+        if (s & RQ_LOCAL_PENDING)
+                return;
+
+        if (req->master_bio) {
+                /* this is data_received (remote read)
+                 * or protocol C P_WRITE_ACK
+                 * or protocol B P_RECV_ACK
+                 * or protocol A "handed_over_to_network" (SendAck)
+                 * or canceled or failed,
+                 * or killed from the transfer log due to connection loss.
+                 */
+
+                /*
+                 * figure out whether to report success or failure.
+                 *
+                 * report success when at least one of the operations succeeded.
+                 * or, to put the other way,
+                 * only report failure, when both operations failed.
+                 *
+                 * what to do about the failures is handled elsewhere.
+                 * what we need to do here is just: complete the master_bio.
+                 *
+                 * local completion error, if any, has been stored as ERR_PTR
+                 * in private_bio within drbd_endio_pri.
+                 */
+                int ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
+                int error = PTR_ERR(req->private_bio);
+
+                /* remove the request from the conflict detection
+                 * respective block_id verification hash */
+                if (!hlist_unhashed(&req->colision))
+                        hlist_del(&req->colision);
+                else
+                        D_ASSERT((s & RQ_NET_MASK) == 0);
+
+                /* for writes we need to do some extra housekeeping */
+                if (rw == WRITE)
+                        _about_to_complete_local_write(mdev, req);
+
+                /* Update disk stats */
+                _drbd_end_io_acct(mdev, req);
+
+                m->error = ok ? 0 : (error ?: -EIO);
+                m->bio = req->master_bio;
+                req->master_bio = NULL;
+        }
+
+        if ((s & RQ_NET_MASK) == 0 || (s & RQ_NET_DONE)) {
+                /* this is disconnected (local only) operation,
+                 * or protocol C P_WRITE_ACK,
+                 * or protocol A or B P_BARRIER_ACK,
+                 * or killed from the transfer log due to connection loss. */
+                _req_is_done(mdev, req, rw);
+        }
+        /* else: network part and not DONE yet. that is
+         * protocol A or B, barrier ack still pending... */
+}
+
+/*
+ * checks whether there was an overlapping request
+ * or ee already registered.
+ *
+ * if so, return 1, in which case this request is completed on the spot,
+ * without ever being submitted or send.
+ *
+ * return 0 if it is ok to submit this request.
+ *
+ * NOTE:
+ * paranoia: assume something above us is broken, and issues different write
+ * requests for the same block simultaneously...
+ *
+ * To ensure these won't be reordered differently on both nodes, resulting in
+ * diverging data sets, we discard the later one(s). Not that this is supposed
+ * to happen, but this is the rationale why we also have to check for
+ * conflicting requests with local origin, and why we have to do so regardless
+ * of whether we allowed multiple primaries.
+ *
+ * BTW, in case we only have one primary, the ee_hash is empty anyways, and the
+ * second hlist_for_each_entry becomes a noop. This is even simpler than to
+ * grab a reference on the net_conf, and check for the two_primaries flag...
+ */
+static int _req_conflicts(struct drbd_request *req)
+{
+        struct drbd_conf *mdev = req->mdev;
+        const sector_t sector = req->sector;
+        const int size = req->size;
+        struct drbd_request *i;
+        struct drbd_epoch_entry *e;
+        struct hlist_node *n;
+        struct hlist_head *slot;
+
+        D_ASSERT(hlist_unhashed(&req->colision));
+
+        if (!get_net_conf(mdev))
+                return 0;
+
+        /* BUG_ON */
+        ERR_IF (mdev->tl_hash_s == 0)
+                goto out_no_conflict;
+        BUG_ON(mdev->tl_hash == NULL);
+
+#define OVERLAPS overlaps(i->sector, i->size, sector, size)
+        slot = tl_hash_slot(mdev, sector);
+        hlist_for_each_entry(i, n, slot, colision) {
+                if (OVERLAPS) {
+                        dev_alert(DEV, "%s[%u] Concurrent local write detected! "
+                              "[DISCARD L] new: %llus +%u; "
+                              "pending: %llus +%u\n",
+                              current->comm, current->pid,
+                              (unsigned long long)sector, size,
+                              (unsigned long long)i->sector, i->size);
+                        goto out_conflict;
+                }
+        }
+
+        if (mdev->ee_hash_s) {
+                /* now, check for overlapping requests with remote origin */
+                BUG_ON(mdev->ee_hash == NULL);
+#undef OVERLAPS
+#define OVERLAPS overlaps(e->sector, e->size, sector, size)
+                slot = ee_hash_slot(mdev, sector);
+                hlist_for_each_entry(e, n, slot, colision) {
+                        if (OVERLAPS) {
+                                dev_alert(DEV, "%s[%u] Concurrent remote write detected!"
+                                      " [DISCARD L] new: %llus +%u; "
+                                      "pending: %llus +%u\n",
+                                      current->comm, current->pid,
+                                      (unsigned long long)sector, size,
+                                      (unsigned long long)e->sector, e->size);
+                                goto out_conflict;
+                        }
+                }
+        }
+#undef OVERLAPS
+
+out_no_conflict:
+        /* this is like it should be, and what we expected.
+         * our users do behave after all... */
+        put_net_conf(mdev);
+        return 0;
+
+out_conflict:
+        put_net_conf(mdev);
+        return 1;
+}
+
+/* obviously this could be coded as many single functions
+ * instead of one huge switch,
+ * or by putting the code directly in the respective locations
+ * (as it has been before).
+ *
+ * but having it this way
+ *  enforces that it is all in this one place, where it is easier to audit,
+ *  it makes it obvious that whatever "event" "happens" to a request should
+ *  happen "atomically" within the req_lock,
+ *  and it enforces that we have to think in a very structured manner
+ *  about the "events" that may happen to a request during its life time ...
+ */
+void __req_mod(struct drbd_request *req, enum drbd_req_event what,
+                struct bio_and_error *m)
+{
+        struct drbd_conf *mdev = req->mdev;
+        m->bio = NULL;
+
+        trace_drbd_req(req, what, NULL);
+
+        switch (what) {
+        default:
+                dev_err(DEV, "LOGIC BUG in %s:%u\n", __FILE__ , __LINE__);
+                break;
+
+        /* does not happen...
+         * initialization done in drbd_req_new
+        case created:
+                break;
+                */
+
+        case to_be_send: /* via network */
+                /* reached via drbd_make_request_common
+                 * and from w_read_retry_remote */
+                D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+                req->rq_state |= RQ_NET_PENDING;
+                inc_ap_pending(mdev);
+                break;
+
+        case to_be_submitted: /* locally */
+                /* reached via drbd_make_request_common */
+                D_ASSERT(!(req->rq_state & RQ_LOCAL_MASK));
+                req->rq_state |= RQ_LOCAL_PENDING;
+                break;
+
+        case completed_ok:
+                if (bio_data_dir(req->master_bio) == WRITE)
+                        mdev->writ_cnt += req->size>>9;
+                else
+                        mdev->read_cnt += req->size>>9;
+
+                req->rq_state |= (RQ_LOCAL_COMPLETED|RQ_LOCAL_OK);
+                req->rq_state &= ~RQ_LOCAL_PENDING;
+
+                _req_may_be_done(req, m);
+                put_ldev(mdev);
+                break;
+
+        case write_completed_with_error:
+                req->rq_state |= RQ_LOCAL_COMPLETED;
+                req->rq_state &= ~RQ_LOCAL_PENDING;
+
+                dev_alert(DEV, "Local WRITE failed sec=%llus size=%u\n",
+                      (unsigned long long)req->sector, req->size);
+                /* and now: check how to handle local io error. */
+                __drbd_chk_io_error(mdev, FALSE);
+                _req_may_be_done(req, m);
+                put_ldev(mdev);
+                break;
+
+        case read_ahead_completed_with_error:
+                /* it is legal to fail READA */
+                req->rq_state |= RQ_LOCAL_COMPLETED;
+                req->rq_state &= ~RQ_LOCAL_PENDING;
+                _req_may_be_done(req, m);
+                put_ldev(mdev);
+                break;
+
+        case read_completed_with_error:
+                drbd_set_out_of_sync(mdev, req->sector, req->size);
+
+                req->rq_state |= RQ_LOCAL_COMPLETED;
+                req->rq_state &= ~RQ_LOCAL_PENDING;
+
+                dev_alert(DEV, "Local READ failed sec=%llus size=%u\n",
+                      (unsigned long long)req->sector, req->size);
+                /* _req_mod(req,to_be_send); oops, recursion... */
+                D_ASSERT(!(req->rq_state & RQ_NET_MASK));
+                req->rq_state |= RQ_NET_PENDING;
+                inc_ap_pending(mdev);
+
+                __drbd_chk_io_error(mdev, FALSE);
+                put_ldev(mdev);
+                /* NOTE: if we have no connection,
+                 * or know the peer has no good data either,
+                 * then we don't actually need to "queue_for_net_read",
+                 * but we do so anyways, since the drbd_io_error()
+                 * and the potential state change to "Diskless"
+                 * needs to be done from process context */
+
+                /* fall through: _req_mod(req,queue_for_net_read); */
+
+        case queue_for_net_read:
+                /* READ or READA, and
+                 * no local disk,
+                 * or target area marked as invalid,
+                 * or just got an io-error. */
+                /* from drbd_make_request_common
+                 * or from bio_endio during read io-error recovery */
+
+                /* so we can verify the handle in the answer packet
+                 * corresponding hlist_del is in _req_may_be_done() */
+                hlist_add_head(&req->colision, ar_hash_slot(mdev, req->sector));
+
+                set_bit(UNPLUG_REMOTE, &mdev->flags); /* why? */
+
+                D_ASSERT(req->rq_state & RQ_NET_PENDING);
+                req->rq_state |= RQ_NET_QUEUED;
+                req->w.cb = (req->rq_state & RQ_LOCAL_MASK)
+                        ? w_read_retry_remote
+                        : w_send_read_req;
+                drbd_queue_work(&mdev->data.work, &req->w);
+                break;
+
+        case queue_for_net_write:
+                /* assert something? */
+                /* from drbd_make_request_common only */
+
+                hlist_add_head(&req->colision, tl_hash_slot(mdev, req->sector));
+                /* corresponding hlist_del is in _req_may_be_done() */
+
+                /* NOTE
+                 * In case the req ended up on the transfer log before being
+                 * queued on the worker, it could lead to this request being
+                 * missed during cleanup after connection loss.
+                 * So we have to do both operations here,
+                 * within the same lock that protects the transfer log.
+                 *
+                 * _req_add_to_epoch(req); this has to be after the
+                 * _maybe_start_new_epoch(req); which happened in
+                 * drbd_make_request_common, because we now may set the bit
+                 * again ourselves to close the current epoch.
+                 *
+                 * Add req to the (now) current epoch (barrier). */
+
+                /* see drbd_make_request_common,
+                 * just after it grabs the req_lock */
+                D_ASSERT(test_bit(CREATE_BARRIER, &mdev->flags) == 0);
+
+                req->epoch = mdev->newest_tle->br_number;
+                list_add_tail(&req->tl_requests,
+                                &mdev->newest_tle->requests);
+
+                /* increment size of current epoch */
+                mdev->newest_tle->n_req++;
+
+                /* queue work item to send data */
+                D_ASSERT(req->rq_state & RQ_NET_PENDING);
+                req->rq_state |= RQ_NET_QUEUED;
+                req->w.cb =  w_send_dblock;
+                drbd_queue_work(&mdev->data.work, &req->w);
+
+                /* close the epoch, in case it outgrew the limit */
+                if (mdev->newest_tle->n_req >= mdev->net_conf->max_epoch_size)
+                        queue_barrier(mdev);
+
+                break;
+
+        case send_canceled:
+                /* treat it the same */
+        case send_failed:
+                /* real cleanup will be done from tl_clear.  just update flags
+                 * so it is no longer marked as on the worker queue */
+                req->rq_state &= ~RQ_NET_QUEUED;
+                /* if we did it right, tl_clear should be scheduled only after
+                 * this, so this should not be necessary! */
+                _req_may_be_done(req, m);
+                break;
+
+        case handed_over_to_network:
+                /* assert something? */
+                if (bio_data_dir(req->master_bio) == WRITE &&
+                    mdev->net_conf->wire_protocol == DRBD_PROT_A) {
+                        /* this is what is dangerous about protocol A:
+                         * pretend it was successfully written on the peer. */
+                        if (req->rq_state & RQ_NET_PENDING) {
+                                dec_ap_pending(mdev);
+                                req->rq_state &= ~RQ_NET_PENDING;
+                                req->rq_state |= RQ_NET_OK;
+                        } /* else: neg-ack was faster... */
+                        /* it is still not yet RQ_NET_DONE until the
+                         * corresponding epoch barrier got acked as well,
+                         * so we know what to dirty on connection loss */
+                }
+                req->rq_state &= ~RQ_NET_QUEUED;
+                req->rq_state |= RQ_NET_SENT;
+                /* because _drbd_send_zc_bio could sleep, and may want to
+                 * dereference the bio even after the "write_acked_by_peer" and
+                 * "completed_ok" events came in, once we return from
+                 * _drbd_send_zc_bio (drbd_send_dblock), we have to check
+                 * whether it is done already, and end it.  */
+                _req_may_be_done(req, m);
+                break;
+
+        case connection_lost_while_pending:
+                /* transfer log cleanup after connection loss */
+                /* assert something? */
+                if (req->rq_state & RQ_NET_PENDING)
+                        dec_ap_pending(mdev);
+                req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+                req->rq_state |= RQ_NET_DONE;
+                /* if it is still queued, we may not complete it here.
+                 * it will be canceled soon. */
+                if (!(req->rq_state & RQ_NET_QUEUED))
+                        _req_may_be_done(req, m);
+                break;
+
+        case write_acked_by_peer_and_sis:
+                req->rq_state |= RQ_NET_SIS;
+        case conflict_discarded_by_peer:
+                /* for discarded conflicting writes of multiple primaries,
+                 * there is no need to keep anything in the tl, potential
+                 * node crashes are covered by the activity log. */
+                if (what == conflict_discarded_by_peer)
+                        dev_alert(DEV, "Got DiscardAck packet %llus +%u!"
+                              " DRBD is not a random data generator!\n",
+                              (unsigned long long)req->sector, req->size);
+                req->rq_state |= RQ_NET_DONE;
+                /* fall through */
+        case write_acked_by_peer:
+                /* protocol C; successfully written on peer.
+                 * Nothing to do here.
+                 * We want to keep the tl in place for all protocols, to cater
+                 * for volatile write-back caches on lower level devices.
+                 *
+                 * A barrier request is expected to have forced all prior
+                 * requests onto stable storage, so completion of a barrier
+                 * request could set NET_DONE right here, and not wait for the
+                 * P_BARRIER_ACK, but that is an unnecessary optimization. */
+
+                /* this makes it effectively the same as for: */
+        case recv_acked_by_peer:
+                /* protocol B; pretends to be successfully written on peer.
+                 * see also notes above in handed_over_to_network about
+                 * protocol != C */
+                req->rq_state |= RQ_NET_OK;
+                D_ASSERT(req->rq_state & RQ_NET_PENDING);
+                dec_ap_pending(mdev);
+                req->rq_state &= ~RQ_NET_PENDING;
+                _req_may_be_done(req, m);
+                break;
+
+        case neg_acked:
+                /* assert something? */
+                if (req->rq_state & RQ_NET_PENDING)
+                        dec_ap_pending(mdev);
+                req->rq_state &= ~(RQ_NET_OK|RQ_NET_PENDING);
+
+                req->rq_state |= RQ_NET_DONE;
+                _req_may_be_done(req, m);
+                /* else: done by handed_over_to_network */
+                break;
+
+        case barrier_acked:
+                if (req->rq_state & RQ_NET_PENDING) {
+                        /* barrier came in before all requests have been acked.
+                         * this is bad, because if the connection is lost now,
+                         * we won't be able to clean them up... */
+                        dev_err(DEV, "FIXME (barrier_acked but pending)\n");
+                        trace_drbd_req(req, nothing, "FIXME (barrier_acked but pending)");
+                        list_move(&req->tl_requests, &mdev->out_of_sequence_requests);
+                }
+                D_ASSERT(req->rq_state & RQ_NET_SENT);
+                req->rq_state |= RQ_NET_DONE;
+                _req_may_be_done(req, m);
+                break;
+
+        case data_received:
+                D_ASSERT(req->rq_state & RQ_NET_PENDING);
+                dec_ap_pending(mdev);
+                req->rq_state &= ~RQ_NET_PENDING;
+                req->rq_state |= (RQ_NET_OK|RQ_NET_DONE);
+                _req_may_be_done(req, m);
+                break;
+        };
+}
+
+/* we may do a local read if:
+ * - we are consistent (of course),
+ * - or we are generally inconsistent,
+ *   BUT we are still/already IN SYNC for this area.
+ *   since size may be bigger than BM_BLOCK_SIZE,
+ *   we may need to check several bits.
+ */
+static int drbd_may_do_local_read(struct drbd_conf *mdev, sector_t sector, int size)
+{
+        unsigned long sbnr, ebnr;
+        sector_t esector, nr_sectors;
+
+        if (mdev->state.disk == D_UP_TO_DATE)
+                return 1;
+        if (mdev->state.disk >= D_OUTDATED)
+                return 0;
+        if (mdev->state.disk <  D_INCONSISTENT)
+                return 0;
+        /* state.disk == D_INCONSISTENT   We will have a look at the BitMap */
+        nr_sectors = drbd_get_capacity(mdev->this_bdev);
+        esector = sector + (size >> 9) - 1;
+
+        D_ASSERT(sector  < nr_sectors);
+        D_ASSERT(esector < nr_sectors);
+
+        sbnr = BM_SECT_TO_BIT(sector);
+        ebnr = BM_SECT_TO_BIT(esector);
+
+        return 0 == drbd_bm_count_bits(mdev, sbnr, ebnr);
+}
+
+static int drbd_make_request_common(struct drbd_conf *mdev, struct bio *bio)
+{
+        const int rw = bio_rw(bio);
+        const int size = bio->bi_size;
+        const sector_t sector = bio->bi_sector;
+        struct drbd_tl_epoch *b = NULL;
+        struct drbd_request *req;
+        int local, remote;
+        int err = -EIO;
+
+        /* allocate outside of all locks; */
+        req = drbd_req_new(mdev, bio);
+        if (!req) {
+                dec_ap_bio(mdev);
+                /* only pass the error to the upper layers.
+                 * if user cannot handle io errors, that's not our business. */
+                dev_err(DEV, "could not kmalloc() req\n");
+                bio_endio(bio, -ENOMEM);
+                return 0;
+        }
+
+        trace_drbd_bio(mdev, "Rq", bio, 0, req);
+
+        local = get_ldev(mdev);
+        if (!local) {
+                bio_put(req->private_bio); /* or we get a bio leak */
+                req->private_bio = NULL;
+        }
+        if (rw == WRITE) {
+                remote = 1;
+        } else {
+                /* READ || READA */
+                if (local) {
+                        if (!drbd_may_do_local_read(mdev, sector, size)) {
+                                /* we could kick the syncer to
+                                 * sync this extent asap, wait for
+                                 * it, then continue locally.
+                                 * Or just issue the request remotely.
+                                 */
+                                local = 0;
+                                bio_put(req->private_bio);
+                                req->private_bio = NULL;
+                                put_ldev(mdev);
+                        }
+                }
+                remote = !local && mdev->state.pdsk >= D_UP_TO_DATE;
+        }
+
+        /* If we have a disk, but a READA request is mapped to remote,
+         * we are R_PRIMARY, D_INCONSISTENT, SyncTarget.
+         * Just fail that READA request right here.
+         *
+         * THINK: maybe fail all READA when not local?
+         *        or make this configurable...
+         *        if network is slow, READA won't do any good.
+         */
+        if (rw == READA && mdev->state.disk >= D_INCONSISTENT && !local) {
+                err = -EWOULDBLOCK;
+                goto fail_and_free_req;
+        }
+
+        /* For WRITES going to the local disk, grab a reference on the target
+         * extent.  This waits for any resync activity in the corresponding
+         * resync extent to finish, and, if necessary, pulls in the target
+         * extent into the activity log, which involves further disk io because
+         * of transactional on-disk meta data updates. */
+        if (rw == WRITE && local)
+                drbd_al_begin_io(mdev, sector);
+
+        remote = remote && (mdev->state.pdsk == D_UP_TO_DATE ||
+                            (mdev->state.pdsk == D_INCONSISTENT &&
+                             mdev->state.conn >= C_CONNECTED));
+
+        if (!(local || remote)) {
+                dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+                goto fail_free_complete;
+        }
+
+        /* For WRITE request, we have to make sure that we have an
+         * unused_spare_tle, in case we need to start a new epoch.
+         * I try to be smart and avoid to pre-allocate always "just in case",
+         * but there is a race between testing the bit and pointer outside the
+         * spinlock, and grabbing the spinlock.
+         * if we lost that race, we retry.  */
+        if (rw == WRITE && remote &&
+            mdev->unused_spare_tle == NULL &&
+            test_bit(CREATE_BARRIER, &mdev->flags)) {
+allocate_barrier:
+                b = kmalloc(sizeof(struct drbd_tl_epoch), GFP_NOIO);
+                if (!b) {
+                        dev_err(DEV, "Failed to alloc barrier.\n");
+                        err = -ENOMEM;
+                        goto fail_free_complete;
+                }
+        }
+
+        /* GOOD, everything prepared, grab the spin_lock */
+        spin_lock_irq(&mdev->req_lock);
+
+        if (remote) {
+                remote = (mdev->state.pdsk == D_UP_TO_DATE ||
+                            (mdev->state.pdsk == D_INCONSISTENT &&
+                             mdev->state.conn >= C_CONNECTED));
+                if (!remote)
+                        dev_warn(DEV, "lost connection while grabbing the req_lock!\n");
+                if (!(local || remote)) {
+                        dev_err(DEV, "IO ERROR: neither local nor remote disk\n");
+                        spin_unlock_irq(&mdev->req_lock);
+                        goto fail_free_complete;
+                }
+        }
+
+        if (b && mdev->unused_spare_tle == NULL) {
+                mdev->unused_spare_tle = b;
+                b = NULL;
+        }
+        if (rw == WRITE && remote &&
+            mdev->unused_spare_tle == NULL &&
+            test_bit(CREATE_BARRIER, &mdev->flags)) {
+                /* someone closed the current epoch
+                 * while we were grabbing the spinlock */
+                spin_unlock_irq(&mdev->req_lock);
+                goto allocate_barrier;
+        }
+
+
+        /* Update disk stats */
+        _drbd_start_io_acct(mdev, req, bio);
+
+        /* _maybe_start_new_epoch(mdev);
+         * If we need to generate a write barrier packet, we have to add the
+         * new epoch (barrier) object, and queue the barrier packet for sending,
+         * and queue the req's data after it _within the same lock_, otherwise
+         * we have race conditions were the reorder domains could be mixed up.
+         *
+         * Even read requests may start a new epoch and queue the corresponding
+         * barrier packet.  To get the write ordering right, we only have to
+         * make sure that, if this is a write request and it triggered a
+         * barrier packet, this request is queued within the same spinlock. */
+        if (remote && mdev->unused_spare_tle &&
+            test_and_clear_bit(CREATE_BARRIER, &mdev->flags)) {
+                _tl_add_barrier(mdev, mdev->unused_spare_tle);
+                mdev->unused_spare_tle = NULL;
+        } else {
+                D_ASSERT(!(remote && rw == WRITE &&
+                           test_bit(CREATE_BARRIER, &mdev->flags)));
+        }
+
+        /* NOTE
+         * Actually, 'local' may be wrong here already, since we may have failed
+         * to write to the meta data, and may become wrong anytime because of
+         * local io-error for some other request, which would lead to us
+         * "detaching" the local disk.
+         *
+         * 'remote' may become wrong any time because the network could fail.
+         *
+         * This is a harmless race condition, though, since it is handled
+         * correctly at the appropriate places; so it just defers the failure
+         * of the respective operation.
+         */
+
+        /* mark them early for readability.
+         * this just sets some state flags. */
+        if (remote)
+                _req_mod(req, to_be_send);
+        if (local)
+                _req_mod(req, to_be_submitted);
+
+        /* check this request on the collision detection hash tables.
+         * if we have a conflict, just complete it here.
+         * THINK do we want to check reads, too? (I don't think so...) */
+        if (rw == WRITE && _req_conflicts(req)) {
+                /* this is a conflicting request.
+                 * even though it may have been only _partially_
+                 * overlapping with one of the currently pending requests,
+                 * without even submitting or sending it, we will
+                 * pretend that it was successfully served right now.
+                 */
+                if (local) {
+                        bio_put(req->private_bio);
+                        req->private_bio = NULL;
+                        drbd_al_complete_io(mdev, req->sector);
+                        put_ldev(mdev);
+                        local = 0;
+                }
+                if (remote)
+                        dec_ap_pending(mdev);
+                _drbd_end_io_acct(mdev, req);
+                /* THINK: do we want to fail it (-EIO), or pretend success? */
+                bio_endio(req->master_bio, 0);
+                req->master_bio = NULL;
+                dec_ap_bio(mdev);
+                drbd_req_free(req);
+                remote = 0;
+        }
+
+        /* NOTE remote first: to get the concurrent write detection right,
+         * we must register the request before start of local IO.  */
+        if (remote) {
+                /* either WRITE and C_CONNECTED,
+                 * or READ, and no local disk,
+                 * or READ, but not in sync.
+                 */
+                _req_mod(req, (rw == WRITE)
+                                ? queue_for_net_write
+                                : queue_for_net_read);
+        }
+        spin_unlock_irq(&mdev->req_lock);
+        kfree(b); /* if someone else has beaten us to it... */
+
+        if (local) {
+                req->private_bio->bi_bdev = mdev->ldev->backing_bdev;
+
+                trace_drbd_bio(mdev, "Pri", req->private_bio, 0, NULL);
+
+                if (FAULT_ACTIVE(mdev, rw == WRITE ? DRBD_FAULT_DT_WR
+                                     : rw == READ  ? DRBD_FAULT_DT_RD
+                                     :               DRBD_FAULT_DT_RA))
+                        bio_endio(req->private_bio, -EIO);
+                else
+                        generic_make_request(req->private_bio);
+        }
+
+        /* we need to plug ALWAYS since we possibly need to kick lo_dev.
+         * we plug after submit, so we won't miss an unplug event */
+        drbd_plug_device(mdev);
+
+        return 0;
+
+fail_free_complete:
+        if (rw == WRITE && local)
+                drbd_al_complete_io(mdev, sector);
+fail_and_free_req:
+        if (local) {
+                bio_put(req->private_bio);
+                req->private_bio = NULL;
+                put_ldev(mdev);
+        }
+        bio_endio(bio, err);
+        drbd_req_free(req);
+        dec_ap_bio(mdev);
+        kfree(b);
+
+        return 0;
+}
+
+/* helper function for drbd_make_request
+ * if we can determine just by the mdev (state) that this request will fail,
+ * return 1
+ * otherwise return 0
+ */
+static int drbd_fail_request_early(struct drbd_conf *mdev, int is_write)
+{
+        /* Unconfigured */
+        if (mdev->state.conn == C_DISCONNECTING &&
+            mdev->state.disk == D_DISKLESS)
+                return 1;
+
+        if (mdev->state.role != R_PRIMARY &&
+                (!allow_oos || is_write)) {
+                if (__ratelimit(&drbd_ratelimit_state)) {
+                        dev_err(DEV, "Process %s[%u] tried to %s; "
+                            "since we are not in Primary state, "
+                            "we cannot allow this\n",
+                            current->comm, current->pid,
+                            is_write ? "WRITE" : "READ");
+                }
+                return 1;
+        }
+
+        /*
+         * Paranoia: we might have been primary, but sync target, or
+         * even diskless, then lost the connection.
+         * This should have been handled (panic? suspend?) somewhere
+         * else. But maybe it was not, so check again here.
+         * Caution: as long as we do not have a read/write lock on mdev,
+         * to serialize state changes, this is racy, since we may lose
+         * the connection *after* we test for the cstate.
+         */
+        if (mdev->state.disk < D_UP_TO_DATE && mdev->state.pdsk < D_UP_TO_DATE) {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Sorry, I have no access to good data anymore.\n");
+                return 1;
+        }
+
+        return 0;
+}
+
+int drbd_make_request_26(struct request_queue *q, struct bio *bio)
+{
+        unsigned int s_enr, e_enr;
+        struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+
+        if (drbd_fail_request_early(mdev, bio_data_dir(bio) & WRITE)) {
+                bio_endio(bio, -EPERM);
+                return 0;
+        }
+
+        /* Reject barrier requests if we know the underlying device does
+         * not support them.
+         * XXX: Need to get this info from peer as well some how so we
+         * XXX: reject if EITHER side/data/metadata area does not support them.
+         *
+         * because of those XXX, this is not yet enabled,
+         * i.e. in drbd_init_set_defaults we set the NO_BARRIER_SUPP bit.
+         */
+        if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER) && test_bit(NO_BARRIER_SUPP, &mdev->flags))) {
+                /* dev_warn(DEV, "Rejecting barrier request as underlying device does not support\n"); */
+                bio_endio(bio, -EOPNOTSUPP);
+                return 0;
+        }
+
+        /*
+         * what we "blindly" assume:
+         */
+        D_ASSERT(bio->bi_size > 0);
+        D_ASSERT((bio->bi_size & 0x1ff) == 0);
+        D_ASSERT(bio->bi_idx == 0);
+
+        /* to make some things easier, force alignment of requests within the
+         * granularity of our hash tables */
+        s_enr = bio->bi_sector >> HT_SHIFT;
+        e_enr = (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT;
+
+        if (likely(s_enr == e_enr)) {
+                inc_ap_bio(mdev, 1);
+                return drbd_make_request_common(mdev, bio);
+        }
+
+        /* can this bio be split generically?
+         * Maybe add our own split-arbitrary-bios function. */
+        if (bio->bi_vcnt != 1 || bio->bi_idx != 0 || bio->bi_size > DRBD_MAX_SEGMENT_SIZE) {
+                /* rather error out here than BUG in bio_split */
+                dev_err(DEV, "bio would need to, but cannot, be split: "
+                    "(vcnt=%u,idx=%u,size=%u,sector=%llu)\n",
+                    bio->bi_vcnt, bio->bi_idx, bio->bi_size,
+                    (unsigned long long)bio->bi_sector);
+                bio_endio(bio, -EINVAL);
+        } else {
+                /* This bio crosses some boundary, so we have to split it. */
+                struct bio_pair *bp;
+                /* works for the "do not cross hash slot boundaries" case
+                 * e.g. sector 262269, size 4096
+                 * s_enr = 262269 >> 6 = 4097
+                 * e_enr = (262269+8-1) >> 6 = 4098
+                 * HT_SHIFT = 6
+                 * sps = 64, mask = 63
+                 * first_sectors = 64 - (262269 & 63) = 3
+                 */
+                const sector_t sect = bio->bi_sector;
+                const int sps = 1 << HT_SHIFT; /* sectors per slot */
+                const int mask = sps - 1;
+                const sector_t first_sectors = sps - (sect & mask);
+                bp = bio_split(bio,
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,28)
+                                bio_split_pool,
+#endif
+                                first_sectors);
+
+                /* we need to get a "reference count" (ap_bio_cnt)
+                 * to avoid races with the disconnect/reconnect/suspend code.
+                 * In case we need to split the bio here, we need to get two references
+                 * atomically, otherwise we might deadlock when trying to submit the
+                 * second one! */
+                inc_ap_bio(mdev, 2);
+
+                D_ASSERT(e_enr == s_enr + 1);
+
+                drbd_make_request_common(mdev, &bp->bio1);
+                drbd_make_request_common(mdev, &bp->bio2);
+                bio_pair_release(bp);
+        }
+        return 0;
+}
+
+/* This is called by bio_add_page().  With this function we reduce
+ * the number of BIOs that span over multiple DRBD_MAX_SEGMENT_SIZEs
+ * units (was AL_EXTENTs).
+ *
+ * we do the calculation within the lower 32bit of the byte offsets,
+ * since we don't care for actual offset, but only check whether it
+ * would cross "activity log extent" boundaries.
+ *
+ * As long as the BIO is empty we have to allow at least one bvec,
+ * regardless of size and offset.  so the resulting bio may still
+ * cross extent boundaries.  those are dealt with (bio_split) in
+ * drbd_make_request_26.
+ */
+int drbd_merge_bvec(struct request_queue *q, struct bvec_merge_data *bvm, struct bio_vec *bvec)
+{
+        struct drbd_conf *mdev = (struct drbd_conf *) q->queuedata;
+        unsigned int bio_offset =
+                (unsigned int)bvm->bi_sector << 9; /* 32 bit */
+        unsigned int bio_size = bvm->bi_size;
+        int limit, backing_limit;
+
+        limit = DRBD_MAX_SEGMENT_SIZE
+              - ((bio_offset & (DRBD_MAX_SEGMENT_SIZE-1)) + bio_size);
+        if (limit < 0)
+                limit = 0;
+        if (bio_size == 0) {
+                if (limit <= bvec->bv_len)
+                        limit = bvec->bv_len;
+        } else if (limit && get_ldev(mdev)) {
+                struct request_queue * const b =
+                        mdev->ldev->backing_bdev->bd_disk->queue;
+                if (b->merge_bvec_fn && mdev->ldev->dc.use_bmbv) {
+                        backing_limit = b->merge_bvec_fn(b, bvm, bvec);
+                        limit = min(limit, backing_limit);
+                }
+                put_ldev(mdev);
+        }
+        return limit;
+}
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
new file mode 100644
index 000000000000..d37ab57f1209
--- /dev/null
+++ b/drivers/block/drbd/drbd_req.h
@@ -0,0 +1,327 @@
+/*
+   drbd_req.h
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2006-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2006-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+   Copyright (C) 2006-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+
+   DRBD is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   DRBD is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _DRBD_REQ_H
+#define _DRBD_REQ_H
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+
+#include <linux/slab.h>
+#include <linux/drbd.h>
+#include "drbd_int.h"
+#include "drbd_wrappers.h"
+
+/* The request callbacks will be called in irq context by the IDE drivers,
+   and in Softirqs/Tasklets/BH context by the SCSI drivers,
+   and by the receiver and worker in kernel-thread context.
+   Try to get the locking right :) */
+
+/*
+ * Objects of type struct drbd_request do only exist on a R_PRIMARY node, and are
+ * associated with IO requests originating from the block layer above us.
+ *
+ * There are quite a few things that may happen to a drbd request
+ * during its lifetime.
+ *
+ *  It will be created.
+ *  It will be marked with the intention to be
+ *    submitted to local disk and/or
+ *    send via the network.
+ *
+ *  It has to be placed on the transfer log and other housekeeping lists,
+ *  In case we have a network connection.
+ *
+ *  It may be identified as a concurrent (write) request
+ *    and be handled accordingly.
+ *
+ *  It may me handed over to the local disk subsystem.
+ *  It may be completed by the local disk subsystem,
+ *    either sucessfully or with io-error.
+ *  In case it is a READ request, and it failed locally,
+ *    it may be retried remotely.
+ *
+ *  It may be queued for sending.
+ *  It may be handed over to the network stack,
+ *    which may fail.
+ *  It may be acknowledged by the "peer" according to the wire_protocol in use.
+ *    this may be a negative ack.
+ *  It may receive a faked ack when the network connection is lost and the
+ *  transfer log is cleaned up.
+ *  Sending may be canceled due to network connection loss.
+ *  When it finally has outlived its time,
+ *    corresponding dirty bits in the resync-bitmap may be cleared or set,
+ *    it will be destroyed,
+ *    and completion will be signalled to the originator,
+ *      with or without "success".
+ */
+
+enum drbd_req_event {
+        created,
+        to_be_send,
+        to_be_submitted,
+
+        /* XXX yes, now I am inconsistent...
+         * these two are not "events" but "actions"
+         * oh, well... */
+        queue_for_net_write,
+        queue_for_net_read,
+
+        send_canceled,
+        send_failed,
+        handed_over_to_network,
+        connection_lost_while_pending,
+        recv_acked_by_peer,
+        write_acked_by_peer,
+        write_acked_by_peer_and_sis, /* and set_in_sync */
+        conflict_discarded_by_peer,
+        neg_acked,
+        barrier_acked, /* in protocol A and B */
+        data_received, /* (remote read) */
+
+        read_completed_with_error,
+        read_ahead_completed_with_error,
+        write_completed_with_error,
+        completed_ok,
+        nothing, /* for tracing only */
+};
+
+/* encoding of request states for now.  we don't actually need that many bits.
+ * we don't need to do atomic bit operations either, since most of the time we
+ * need to look at the connection state and/or manipulate some lists at the
+ * same time, so we should hold the request lock anyways.
+ */
+enum drbd_req_state_bits {
+        /* 210
+         * 000: no local possible
+         * 001: to be submitted
+         *    UNUSED, we could map: 011: submitted, completion still pending
+         * 110: completed ok
+         * 010: completed with error
+         */
+        __RQ_LOCAL_PENDING,
+        __RQ_LOCAL_COMPLETED,
+        __RQ_LOCAL_OK,
+
+        /* 76543
+         * 00000: no network possible
+         * 00001: to be send
+         * 00011: to be send, on worker queue
+         * 00101: sent, expecting recv_ack (B) or write_ack (C)
+         * 11101: sent,
+         *        recv_ack (B) or implicit "ack" (A),
+         *        still waiting for the barrier ack.
+         *        master_bio may already be completed and invalidated.
+         * 11100: write_acked (C),
+         *        data_received (for remote read, any protocol)
+         *        or finally the barrier ack has arrived (B,A)...
+         *        request can be freed
+         * 01100: neg-acked (write, protocol C)
+         *        or neg-d-acked (read, any protocol)
+         *        or killed from the transfer log
+         *        during cleanup after connection loss
+         *        request can be freed
+         * 01000: canceled or send failed...
+         *        request can be freed
+         */
+
+        /* if "SENT" is not set, yet, this can still fail or be canceled.
+         * if "SENT" is set already, we still wait for an Ack packet.
+         * when cleared, the master_bio may be completed.
+         * in (B,A) the request object may still linger on the transaction log
+         * until the corresponding barrier ack comes in */
+        __RQ_NET_PENDING,
+
+        /* If it is QUEUED, and it is a WRITE, it is also registered in the
+         * transfer log. Currently we need this flag to avoid conflicts between
+         * worker canceling the request and tl_clear_barrier killing it from
+         * transfer log.  We should restructure the code so this conflict does
+         * no longer occur. */
+        __RQ_NET_QUEUED,
+
+        /* well, actually only "handed over to the network stack".
+         *
+         * TODO can potentially be dropped because of the similar meaning
+         * of RQ_NET_SENT and ~RQ_NET_QUEUED.
+         * however it is not exactly the same. before we drop it
+         * we must ensure that we can tell a request with network part
+         * from a request without, regardless of what happens to it. */
+        __RQ_NET_SENT,
+
+        /* when set, the request may be freed (if RQ_NET_QUEUED is clear).
+         * basically this means the corresponding P_BARRIER_ACK was received */
+        __RQ_NET_DONE,
+
+        /* whether or not we know (C) or pretend (B,A) that the write
+         * was successfully written on the peer.
+         */
+        __RQ_NET_OK,
+
+        /* peer called drbd_set_in_sync() for this write */
+        __RQ_NET_SIS,
+
+        /* keep this last, its for the RQ_NET_MASK */
+        __RQ_NET_MAX,
+};
+
+#define RQ_LOCAL_PENDING   (1UL << __RQ_LOCAL_PENDING)
+#define RQ_LOCAL_COMPLETED (1UL << __RQ_LOCAL_COMPLETED)
+#define RQ_LOCAL_OK        (1UL << __RQ_LOCAL_OK)
+
+#define RQ_LOCAL_MASK      ((RQ_LOCAL_OK << 1)-1) /* 0x07 */
+
+#define RQ_NET_PENDING     (1UL << __RQ_NET_PENDING)
+#define RQ_NET_QUEUED      (1UL << __RQ_NET_QUEUED)
+#define RQ_NET_SENT        (1UL << __RQ_NET_SENT)
+#define RQ_NET_DONE        (1UL << __RQ_NET_DONE)
+#define RQ_NET_OK          (1UL << __RQ_NET_OK)
+#define RQ_NET_SIS         (1UL << __RQ_NET_SIS)
+
+/* 0x1f8 */
+#define RQ_NET_MASK        (((1UL << __RQ_NET_MAX)-1) & ~RQ_LOCAL_MASK)
+
+/* epoch entries */
+static inline
+struct hlist_head *ee_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        BUG_ON(mdev->ee_hash_s == 0);
+        return mdev->ee_hash +
+                ((unsigned int)(sector>>HT_SHIFT) % mdev->ee_hash_s);
+}
+
+/* transfer log (drbd_request objects) */
+static inline
+struct hlist_head *tl_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        BUG_ON(mdev->tl_hash_s == 0);
+        return mdev->tl_hash +
+                ((unsigned int)(sector>>HT_SHIFT) % mdev->tl_hash_s);
+}
+
+/* application reads (drbd_request objects) */
+static struct hlist_head *ar_hash_slot(struct drbd_conf *mdev, sector_t sector)
+{
+        return mdev->app_reads_hash
+                + ((unsigned int)(sector) % APP_R_HSIZE);
+}
+
+/* when we receive the answer for a read request,
+ * verify that we actually know about it */
+static inline struct drbd_request *_ar_id_to_req(struct drbd_conf *mdev,
+        u64 id, sector_t sector)
+{
+        struct hlist_head *slot = ar_hash_slot(mdev, sector);
+        struct hlist_node *n;
+        struct drbd_request *req;
+
+        hlist_for_each_entry(req, n, slot, colision) {
+                if ((unsigned long)req == (unsigned long)id) {
+                        D_ASSERT(req->sector == sector);
+                        return req;
+                }
+        }
+        return NULL;
+}
+
+static inline struct drbd_request *drbd_req_new(struct drbd_conf *mdev,
+        struct bio *bio_src)
+{
+        struct bio *bio;
+        struct drbd_request *req =
+                mempool_alloc(drbd_request_mempool, GFP_NOIO);
+        if (likely(req)) {
+                bio = bio_clone(bio_src, GFP_NOIO); /* XXX cannot fail?? */
+
+                req->rq_state    = 0;
+                req->mdev        = mdev;
+                req->master_bio  = bio_src;
+                req->private_bio = bio;
+                req->epoch       = 0;
+                req->sector      = bio->bi_sector;
+                req->size        = bio->bi_size;
+                req->start_time  = jiffies;
+                INIT_HLIST_NODE(&req->colision);
+                INIT_LIST_HEAD(&req->tl_requests);
+                INIT_LIST_HEAD(&req->w.list);
+
+                bio->bi_private  = req;
+                bio->bi_end_io   = drbd_endio_pri;
+                bio->bi_next     = NULL;
+        }
+        return req;
+}
+
+static inline void drbd_req_free(struct drbd_request *req)
+{
+        mempool_free(req, drbd_request_mempool);
+}
+
+static inline int overlaps(sector_t s1, int l1, sector_t s2, int l2)
+{
+        return !((s1 + (l1>>9) <= s2) || (s1 >= s2 + (l2>>9)));
+}
+
+/* Short lived temporary struct on the stack.
+ * We could squirrel the error to be returned into
+ * bio->bi_size, or similar. But that would be too ugly. */
+struct bio_and_error {
+        struct bio *bio;
+        int error;
+};
+
+extern void _req_may_be_done(struct drbd_request *req,
+                struct bio_and_error *m);
+extern void __req_mod(struct drbd_request *req, enum drbd_req_event what,
+                struct bio_and_error *m);
+extern void complete_master_bio(struct drbd_conf *mdev,
+                struct bio_and_error *m);
+
+/* use this if you don't want to deal with calling complete_master_bio()
+ * outside the spinlock, e.g. when walking some list on cleanup. */
+static inline void _req_mod(struct drbd_request *req, enum drbd_req_event what)
+{
+        struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
+
+        /* __req_mod possibly frees req, do not touch req after that! */
+        __req_mod(req, what, &m);
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+}
+
+/* completion of master bio is outside of spinlock.
+ * If you need it irqsave, do it your self! */
+static inline void req_mod(struct drbd_request *req,
+                enum drbd_req_event what)
+{
+        struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
+        spin_lock_irq(&mdev->req_lock);
+        __req_mod(req, what, &m);
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+}
+#endif
diff --git a/drivers/block/drbd/drbd_strings.c b/drivers/block/drbd/drbd_strings.c
new file mode 100644
index 000000000000..76863e3f05be
--- /dev/null
+++ b/drivers/block/drbd/drbd_strings.c
@@ -0,0 +1,113 @@
+/*
+  drbd.h
+
+  This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+  Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+  Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+  Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+  drbd is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2, or (at your option)
+  any later version.
+
+  drbd is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with drbd; see the file COPYING.  If not, write to
+  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include <linux/drbd.h>
+
+static const char *drbd_conn_s_names[] = {
+        [C_STANDALONE]       = "StandAlone",
+        [C_DISCONNECTING]    = "Disconnecting",
+        [C_UNCONNECTED]      = "Unconnected",
+        [C_TIMEOUT]          = "Timeout",
+        [C_BROKEN_PIPE]      = "BrokenPipe",
+        [C_NETWORK_FAILURE]  = "NetworkFailure",
+        [C_PROTOCOL_ERROR]   = "ProtocolError",
+        [C_WF_CONNECTION]    = "WFConnection",
+        [C_WF_REPORT_PARAMS] = "WFReportParams",
+        [C_TEAR_DOWN]        = "TearDown",
+        [C_CONNECTED]        = "Connected",
+        [C_STARTING_SYNC_S]  = "StartingSyncS",
+        [C_STARTING_SYNC_T]  = "StartingSyncT",
+        [C_WF_BITMAP_S]      = "WFBitMapS",
+        [C_WF_BITMAP_T]      = "WFBitMapT",
+        [C_WF_SYNC_UUID]     = "WFSyncUUID",
+        [C_SYNC_SOURCE]      = "SyncSource",
+        [C_SYNC_TARGET]      = "SyncTarget",
+        [C_PAUSED_SYNC_S]    = "PausedSyncS",
+        [C_PAUSED_SYNC_T]    = "PausedSyncT",
+        [C_VERIFY_S]         = "VerifyS",
+        [C_VERIFY_T]         = "VerifyT",
+};
+
+static const char *drbd_role_s_names[] = {
+        [R_PRIMARY]   = "Primary",
+        [R_SECONDARY] = "Secondary",
+        [R_UNKNOWN]   = "Unknown"
+};
+
+static const char *drbd_disk_s_names[] = {
+        [D_DISKLESS]     = "Diskless",
+        [D_ATTACHING]    = "Attaching",
+        [D_FAILED]       = "Failed",
+        [D_NEGOTIATING]  = "Negotiating",
+        [D_INCONSISTENT] = "Inconsistent",
+        [D_OUTDATED]     = "Outdated",
+        [D_UNKNOWN]      = "DUnknown",
+        [D_CONSISTENT]   = "Consistent",
+        [D_UP_TO_DATE]   = "UpToDate",
+};
+
+static const char *drbd_state_sw_errors[] = {
+        [-SS_TWO_PRIMARIES] = "Multiple primaries not allowed by config",
+        [-SS_NO_UP_TO_DATE_DISK] = "Refusing to be Primary without at least one UpToDate disk",
+        [-SS_NO_LOCAL_DISK] = "Can not resync without local disk",
+        [-SS_NO_REMOTE_DISK] = "Can not resync without remote disk",
+        [-SS_CONNECTED_OUTDATES] = "Refusing to be Outdated while Connected",
+        [-SS_PRIMARY_NOP] = "Refusing to be Primary while peer is not outdated",
+        [-SS_RESYNC_RUNNING] = "Can not start OV/resync since it is already active",
+        [-SS_ALREADY_STANDALONE] = "Can not disconnect a StandAlone device",
+        [-SS_CW_FAILED_BY_PEER] = "State change was refused by peer node",
+        [-SS_IS_DISKLESS] = "Device is diskless, the requested operation requires a disk",
+        [-SS_DEVICE_IN_USE] = "Device is held open by someone",
+        [-SS_NO_NET_CONFIG] = "Have no net/connection configuration",
+        [-SS_NO_VERIFY_ALG] = "Need a verify algorithm to start online verify",
+        [-SS_NEED_CONNECTION] = "Need a connection to start verify or resync",
+        [-SS_NOT_SUPPORTED] = "Peer does not support protocol",
+        [-SS_LOWER_THAN_OUTDATED] = "Disk state is lower than outdated",
+        [-SS_IN_TRANSIENT_STATE] = "In transient state, retry after next state change",
+        [-SS_CONCURRENT_ST_CHG] = "Concurrent state changes detected and aborted",
+};
+
+const char *drbd_conn_str(enum drbd_conns s)
+{
+        /* enums are unsigned... */
+        return s > C_PAUSED_SYNC_T ? "TOO_LARGE" : drbd_conn_s_names[s];
+}
+
+const char *drbd_role_str(enum drbd_role s)
+{
+        return s > R_SECONDARY   ? "TOO_LARGE" : drbd_role_s_names[s];
+}
+
+const char *drbd_disk_str(enum drbd_disk_state s)
+{
+        return s > D_UP_TO_DATE    ? "TOO_LARGE" : drbd_disk_s_names[s];
+}
+
+const char *drbd_set_st_err_str(enum drbd_state_ret_codes err)
+{
+        return err <= SS_AFTER_LAST_ERROR ? "TOO_SMALL" :
+               err > SS_TWO_PRIMARIES ? "TOO_LARGE"
+                        : drbd_state_sw_errors[-err];
+}
diff --git a/drivers/block/drbd/drbd_tracing.c b/drivers/block/drbd/drbd_tracing.c
new file mode 100644
index 000000000000..d18d4f7b4bef
--- /dev/null
+++ b/drivers/block/drbd/drbd_tracing.c
@@ -0,0 +1,752 @@
+/*
+   drbd_tracing.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/module.h>
+#include <linux/drbd.h>
+#include <linux/ctype.h>
+#include "drbd_int.h"
+#include "drbd_tracing.h"
+#include <linux/drbd_tag_magic.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Philipp Reisner, Lars Ellenberg");
+MODULE_DESCRIPTION("DRBD tracepoint probes");
+MODULE_PARM_DESC(trace_mask, "Bitmap of events to trace see drbd_tracing.c");
+MODULE_PARM_DESC(trace_level, "Current tracing level (changeable in /sys)");
+MODULE_PARM_DESC(trace_devs, "Bitmap of devices to trace (changeable in /sys)");
+
+unsigned int trace_mask = 0;  /* Bitmap of events to trace */
+int trace_level;              /* Current trace level */
+int trace_devs;               /* Bitmap of devices to trace */
+
+module_param(trace_mask, uint, 0444);
+module_param(trace_level, int, 0644);
+module_param(trace_devs, int, 0644);
+
+enum {
+        TRACE_PACKET  = 0x0001,
+        TRACE_RQ      = 0x0002,
+        TRACE_UUID    = 0x0004,
+        TRACE_RESYNC  = 0x0008,
+        TRACE_EE      = 0x0010,
+        TRACE_UNPLUG  = 0x0020,
+        TRACE_NL      = 0x0040,
+        TRACE_AL_EXT  = 0x0080,
+        TRACE_INT_RQ  = 0x0100,
+        TRACE_MD_IO   = 0x0200,
+        TRACE_EPOCH   = 0x0400,
+};
+
+/* Buffer printing support
+ * dbg_print_flags: used for Flags arg to drbd_print_buffer
+ * - DBGPRINT_BUFFADDR; if set, each line starts with the
+ *       virtual address of the line being output. If clear,
+ *       each line starts with the offset from the beginning
+ *       of the buffer. */
+enum dbg_print_flags {
+    DBGPRINT_BUFFADDR = 0x0001,
+};
+
+/* Macro stuff */
+static char *nl_packet_name(int packet_type)
+{
+/* Generate packet type strings */
+#define NL_PACKET(name, number, fields) \
+        [P_ ## name] = # name,
+#define NL_INTEGER Argh!
+#define NL_BIT Argh!
+#define NL_INT64 Argh!
+#define NL_STRING Argh!
+
+        static char *nl_tag_name[P_nl_after_last_packet] = {
+#include "linux/drbd_nl.h"
+        };
+
+        return (packet_type < sizeof(nl_tag_name)/sizeof(nl_tag_name[0])) ?
+            nl_tag_name[packet_type] : "*Unknown*";
+}
+/* /Macro stuff */
+
+static inline int is_mdev_trace(struct drbd_conf *mdev, unsigned int level)
+{
+        return trace_level >= level && ((1 << mdev_to_minor(mdev)) & trace_devs);
+}
+
+static void probe_drbd_unplug(struct drbd_conf *mdev, char *msg)
+{
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        dev_info(DEV, "%s, ap_bio_count=%d\n", msg, atomic_read(&mdev->ap_bio_cnt));
+}
+
+static void probe_drbd_uuid(struct drbd_conf *mdev, enum drbd_uuid_index index)
+{
+        static char *uuid_str[UI_EXTENDED_SIZE] = {
+                [UI_CURRENT] = "CURRENT",
+                [UI_BITMAP] = "BITMAP",
+                [UI_HISTORY_START] = "HISTORY_START",
+                [UI_HISTORY_END] = "HISTORY_END",
+                [UI_SIZE] = "SIZE",
+                [UI_FLAGS] = "FLAGS",
+        };
+
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        if (index >= UI_EXTENDED_SIZE) {
+                dev_warn(DEV, " uuid_index >= EXTENDED_SIZE\n");
+                return;
+        }
+
+        dev_info(DEV, " uuid[%s] now %016llX\n",
+                 uuid_str[index],
+                 (unsigned long long)mdev->ldev->md.uuid[index]);
+}
+
+static void probe_drbd_md_io(struct drbd_conf *mdev, int rw,
+                             struct drbd_backing_dev *bdev)
+{
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        dev_info(DEV, " %s metadata superblock now\n",
+                 rw == READ ? "Reading" : "Writing");
+}
+
+static void probe_drbd_ee(struct drbd_conf *mdev, struct drbd_epoch_entry *e, char* msg)
+{
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        dev_info(DEV, "EE %s sec=%llus size=%u e=%p\n",
+                 msg, (unsigned long long)e->sector, e->size, e);
+}
+
+static void probe_drbd_epoch(struct drbd_conf *mdev, struct drbd_epoch *epoch,
+                             enum epoch_event ev)
+{
+        static char *epoch_event_str[] = {
+                [EV_PUT] = "put",
+                [EV_GOT_BARRIER_NR] = "got_barrier_nr",
+                [EV_BARRIER_DONE] = "barrier_done",
+                [EV_BECAME_LAST] = "became_last",
+                [EV_TRACE_FLUSH] = "issuing_flush",
+                [EV_TRACE_ADD_BARRIER] = "added_barrier",
+                [EV_TRACE_SETTING_BI] = "just set barrier_in_next_epoch",
+        };
+
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        ev &= ~EV_CLEANUP;
+
+        switch (ev) {
+        case EV_TRACE_ALLOC:
+                dev_info(DEV, "Allocate epoch %p/xxxx { } nr_epochs=%d\n", epoch, mdev->epochs);
+                break;
+        case EV_TRACE_FREE:
+                dev_info(DEV, "Freeing epoch %p/%d { size=%d } nr_epochs=%d\n",
+                         epoch, epoch->barrier_nr, atomic_read(&epoch->epoch_size),
+                         mdev->epochs);
+                break;
+        default:
+                dev_info(DEV, "Update epoch  %p/%d { size=%d active=%d %c%c n%c%c } ev=%s\n",
+                         epoch, epoch->barrier_nr, atomic_read(&epoch->epoch_size),
+                         atomic_read(&epoch->active),
+                         test_bit(DE_HAVE_BARRIER_NUMBER, &epoch->flags) ? 'n' : '-',
+                         test_bit(DE_CONTAINS_A_BARRIER, &epoch->flags) ? 'b' : '-',
+                         test_bit(DE_BARRIER_IN_NEXT_EPOCH_ISSUED, &epoch->flags) ? 'i' : '-',
+                         test_bit(DE_BARRIER_IN_NEXT_EPOCH_DONE, &epoch->flags) ? 'd' : '-',
+                         epoch_event_str[ev]);
+        }
+}
+
+static void probe_drbd_netlink(void *data, int is_req)
+{
+        struct cn_msg *msg = data;
+
+        if (is_req) {
+                struct drbd_nl_cfg_req *nlp = (struct drbd_nl_cfg_req *)msg->data;
+
+                printk(KERN_INFO "drbd%d: "
+                         "Netlink: << %s (%d) - seq: %x, ack: %x, len: %x\n",
+                         nlp->drbd_minor,
+                         nl_packet_name(nlp->packet_type),
+                         nlp->packet_type,
+                         msg->seq, msg->ack, msg->len);
+        } else {
+                struct drbd_nl_cfg_reply *nlp = (struct drbd_nl_cfg_reply *)msg->data;
+
+                printk(KERN_INFO "drbd%d: "
+                       "Netlink: >> %s (%d) - seq: %x, ack: %x, len: %x\n",
+                       nlp->minor,
+                       nlp->packet_type == P_nl_after_last_packet ?
+                       "Empty-Reply" : nl_packet_name(nlp->packet_type),
+                       nlp->packet_type,
+                       msg->seq, msg->ack, msg->len);
+        }
+}
+
+static void probe_drbd_actlog(struct drbd_conf *mdev, sector_t sector, char* msg)
+{
+        unsigned int enr = (sector >> (AL_EXTENT_SHIFT-9));
+
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        dev_info(DEV, "%s (sec=%llus, al_enr=%u, rs_enr=%d)\n",
+                 msg, (unsigned long long) sector, enr,
+                 (int)BM_SECT_TO_EXT(sector));
+}
+
+/**
+ * drbd_print_buffer() - Hexdump arbitrary binary data into a buffer
+ * @prefix:     String is output at the beginning of each line output.
+ * @flags:      Currently only defined flag: DBGPRINT_BUFFADDR; if set, each
+ *              line starts with the virtual address of the line being
+ *              output. If clear, each line starts with the offset from the
+ *              beginning of the buffer.
+ * @size:       Indicates the size of each entry in the buffer. Supported
+ *              values are sizeof(char), sizeof(short) and sizeof(int)
+ * @buffer:     Start address of buffer
+ * @buffer_va:  Virtual address of start of buffer (normally the same
+ *              as Buffer, but having it separate allows it to hold
+ *              file address for example)
+ * @length:     length of buffer
+ */
+static void drbd_print_buffer(const char *prefix, unsigned int flags, int size,
+                              const void *buffer, const void *buffer_va,
+                              unsigned int length)
+
+#define LINE_SIZE       16
+#define LINE_ENTRIES    (int)(LINE_SIZE/size)
+{
+        const unsigned char *pstart;
+        const unsigned char *pstart_va;
+        const unsigned char *pend;
+        char bytes_str[LINE_SIZE*3+8], ascii_str[LINE_SIZE+8];
+        char *pbytes = bytes_str, *pascii = ascii_str;
+        int  offset = 0;
+        long sizemask;
+        int  field_width;
+        int  index;
+        const unsigned char *pend_str;
+        const unsigned char *p;
+        int count;
+
+        /* verify size parameter */
+        if (size != sizeof(char) &&
+            size != sizeof(short) &&
+            size != sizeof(int)) {
+                printk(KERN_DEBUG "drbd_print_buffer: "
+                        "ERROR invalid size %d\n", size);
+                return;
+        }
+
+        sizemask = size-1;
+        field_width = size*2;
+
+        /* Adjust start/end to be on appropriate boundary for size */
+        buffer = (const char *)((long)buffer & ~sizemask);
+        pend   = (const unsigned char *)
+                (((long)buffer + length + sizemask) & ~sizemask);
+
+        if (flags & DBGPRINT_BUFFADDR) {
+                /* Move start back to nearest multiple of line size,
+                 * if printing address. This results in nicely formatted output
+                 * with addresses being on line size (16) byte boundaries */
+                pstart = (const unsigned char *)((long)buffer & ~(LINE_SIZE-1));
+        } else {
+                pstart = (const unsigned char *)buffer;
+        }
+
+        /* Set value of start VA to print if addresses asked for */
+        pstart_va = (const unsigned char *)buffer_va
+                 - ((const unsigned char *)buffer-pstart);
+
+        /* Calculate end position to nicely align right hand side */
+        pend_str = pstart + (((pend-pstart) + LINE_SIZE-1) & ~(LINE_SIZE-1));
+
+        /* Init strings */
+        *pbytes = *pascii = '\0';
+
+        /* Start at beginning of first line */
+        p = pstart;
+        count = 0;
+
+        while (p < pend_str) {
+                if (p < (const unsigned char *)buffer || p >= pend) {
+                        /* Before start of buffer or after end- print spaces */
+                        pbytes += sprintf(pbytes, "%*c ", field_width, ' ');
+                        pascii += sprintf(pascii, "%*c", size, ' ');
+                        p += size;
+                } else {
+                        /* Add hex and ascii to strings */
+                        int val;
+                        switch (size) {
+                        default:
+                        case 1:
+                                val = *(unsigned char *)p;
+                                break;
+                        case 2:
+                                val = *(unsigned short *)p;
+                                break;
+                        case 4:
+                                val = *(unsigned int *)p;
+                                break;
+                        }
+
+                        pbytes += sprintf(pbytes, "%0*x ", field_width, val);
+
+                        for (index = size; index; index--) {
+                                *pascii++ = isprint(*p) ? *p : '.';
+                                p++;
+                        }
+                }
+
+                count++;
+
+                if (count == LINE_ENTRIES || p >= pend_str) {
+                        /* Null terminate and print record */
+                        *pascii = '\0';
+                        printk(KERN_DEBUG "%s%8.8lx: %*s|%*s|\n",
+                               prefix,
+                               (flags & DBGPRINT_BUFFADDR)
+                               ? (long)pstart_va:(long)offset,
+                               LINE_ENTRIES*(field_width+1), bytes_str,
+                               LINE_SIZE, ascii_str);
+
+                        /* Move onto next line */
+                        pstart_va += (p-pstart);
+                        pstart = p;
+                        count  = 0;
+                        offset += LINE_SIZE;
+
+                        /* Re-init strings */
+                        pbytes = bytes_str;
+                        pascii = ascii_str;
+                        *pbytes = *pascii = '\0';
+                }
+        }
+}
+
+static void probe_drbd_resync(struct drbd_conf *mdev, int level, const char *fmt, va_list args)
+{
+        char str[256];
+
+        if (!is_mdev_trace(mdev, level))
+                return;
+
+        if (vsnprintf(str, 256, fmt, args) >= 256)
+                str[255] = 0;
+
+        printk(KERN_INFO "%s %s: %s", dev_driver_string(disk_to_dev(mdev->vdisk)),
+               dev_name(disk_to_dev(mdev->vdisk)), str);
+}
+
+static void probe_drbd_bio(struct drbd_conf *mdev, const char *pfx, struct bio *bio, int complete,
+                           struct drbd_request *r)
+{
+#if defined(CONFIG_LBDAF) || defined(CONFIG_LBD)
+#define SECTOR_FORMAT "%Lx"
+#else
+#define SECTOR_FORMAT "%lx"
+#endif
+#define SECTOR_SHIFT 9
+
+        unsigned long lowaddr = (unsigned long)(bio->bi_sector << SECTOR_SHIFT);
+        char *faddr = (char *)(lowaddr);
+        char rb[sizeof(void *)*2+6] = { 0, };
+        struct bio_vec *bvec;
+        int segno;
+
+        const int rw = bio->bi_rw;
+        const int biorw      = (rw & (RW_MASK|RWA_MASK));
+        const int biobarrier = (rw & (1<<BIO_RW_BARRIER));
+        const int biosync = (rw & ((1<<BIO_RW_UNPLUG) | (1<<BIO_RW_SYNCIO)));
+
+        if (!is_mdev_trace(mdev, TRACE_LVL_ALWAYS))
+                return;
+
+        if (r)
+                sprintf(rb, "Req:%p ", r);
+
+        dev_info(DEV, "%s %s:%s%s%s Bio:%p %s- %soffset " SECTOR_FORMAT ", size %x\n",
+                 complete ? "<<<" : ">>>",
+                 pfx,
+                 biorw == WRITE ? "Write" : "Read",
+                 biobarrier ? " : B" : "",
+                 biosync ? " : S" : "",
+                 bio,
+                 rb,
+                 complete ? (bio_flagged(bio, BIO_UPTODATE) ? "Success, " : "Failed, ") : "",
+                 bio->bi_sector << SECTOR_SHIFT,
+                 bio->bi_size);
+
+        if (trace_level >= TRACE_LVL_METRICS &&
+            ((biorw == WRITE) ^ complete)) {
+                printk(KERN_DEBUG "  ind     page   offset   length\n");
+                __bio_for_each_segment(bvec, bio, segno, 0) {
+                        printk(KERN_DEBUG "  [%d] %p %8.8x %8.8x\n", segno,
+                               bvec->bv_page, bvec->bv_offset, bvec->bv_len);
+
+                        if (trace_level >= TRACE_LVL_ALL) {
+                                char *bvec_buf;
+                                unsigned long flags;
+
+                                bvec_buf = bvec_kmap_irq(bvec, &flags);
+
+                                drbd_print_buffer("    ", DBGPRINT_BUFFADDR, 1,
+                                                  bvec_buf,
+                                                  faddr,
+                                                  (bvec->bv_len <= 0x80)
+                                                  ? bvec->bv_len : 0x80);
+
+                                bvec_kunmap_irq(bvec_buf, &flags);
+
+                                if (bvec->bv_len > 0x40)
+                                        printk(KERN_DEBUG "    ....\n");
+
+                                faddr += bvec->bv_len;
+                        }
+                }
+        }
+}
+
+static void probe_drbd_req(struct drbd_request *req, enum drbd_req_event what, char *msg)
+{
+        static const char *rq_event_names[] = {
+                [created] = "created",
+                [to_be_send] = "to_be_send",
+                [to_be_submitted] = "to_be_submitted",
+                [queue_for_net_write] = "queue_for_net_write",
+                [queue_for_net_read] = "queue_for_net_read",
+                [send_canceled] = "send_canceled",
+                [send_failed] = "send_failed",
+                [handed_over_to_network] = "handed_over_to_network",
+                [connection_lost_while_pending] =
+                                        "connection_lost_while_pending",
+                [recv_acked_by_peer] = "recv_acked_by_peer",
+                [write_acked_by_peer] = "write_acked_by_peer",
+                [neg_acked] = "neg_acked",
+                [conflict_discarded_by_peer] = "conflict_discarded_by_peer",
+                [barrier_acked] = "barrier_acked",
+                [data_received] = "data_received",
+                [read_completed_with_error] = "read_completed_with_error",
+                [read_ahead_completed_with_error] = "reada_completed_with_error",
+                [write_completed_with_error] = "write_completed_with_error",
+                [completed_ok] = "completed_ok",
+        };
+
+        struct drbd_conf *mdev = req->mdev;
+
+        const int rw = (req->master_bio == NULL ||
+                        bio_data_dir(req->master_bio) == WRITE) ?
+                'W' : 'R';
+        const unsigned long s = req->rq_state;
+
+        if (what != nothing) {
+                dev_info(DEV, "__req_mod(%p %c ,%s)\n", req, rw, rq_event_names[what]);
+        } else {
+                dev_info(DEV, "%s %p %c L%c%c%cN%c%c%c%c%c %u (%llus +%u) %s\n",
+                         msg, req, rw,
+                         s & RQ_LOCAL_PENDING ? 'p' : '-',
+                         s & RQ_LOCAL_COMPLETED ? 'c' : '-',
+                         s & RQ_LOCAL_OK ? 'o' : '-',
+                         s & RQ_NET_PENDING ? 'p' : '-',
+                         s & RQ_NET_QUEUED ? 'q' : '-',
+                         s & RQ_NET_SENT ? 's' : '-',
+                         s & RQ_NET_DONE ? 'd' : '-',
+                         s & RQ_NET_OK ? 'o' : '-',
+                         req->epoch,
+                         (unsigned long long)req->sector,
+                         req->size,
+                         drbd_conn_str(mdev->state.conn));
+        }
+}
+
+
+#define drbd_peer_str drbd_role_str
+#define drbd_pdsk_str drbd_disk_str
+
+#define PSM(A)                                                  \
+do {                                                            \
+        if (mask.A) {                                           \
+                int i = snprintf(p, len, " " #A "( %s )",       \
+                                 drbd_##A##_str(val.A));        \
+                if (i >= len)                                   \
+                        return op;                              \
+                p += i;                                         \
+                len -= i;                                       \
+        }                                                       \
+} while (0)
+
+static char *dump_st(char *p, int len, union drbd_state mask, union drbd_state val)
+{
+        char *op = p;
+        *p = '\0';
+        PSM(role);
+        PSM(peer);
+        PSM(conn);
+        PSM(disk);
+        PSM(pdsk);
+
+        return op;
+}
+
+#define INFOP(fmt, args...) \
+do { \
+        if (trace_level >= TRACE_LVL_ALL) { \
+                dev_info(DEV, "%s:%d: %s [%d] %s %s " fmt , \
+                     file, line, current->comm, current->pid, \
+                     sockname, recv ? "<<<" : ">>>" , \
+                     ## args); \
+        } else { \
+                dev_info(DEV, "%s %s " fmt, sockname, \
+                     recv ? "<<<" : ">>>" , \
+                     ## args); \
+        } \
+} while (0)
+
+static char *_dump_block_id(u64 block_id, char *buff)
+{
+        if (is_syncer_block_id(block_id))
+                strcpy(buff, "SyncerId");
+        else
+                sprintf(buff, "%llx", (unsigned long long)block_id);
+
+        return buff;
+}
+
+static void probe_drbd_packet(struct drbd_conf *mdev, struct socket *sock,
+                              int recv, union p_polymorph *p, char *file, int line)
+{
+        char *sockname = sock == mdev->meta.socket ? "meta" : "data";
+        int cmd = (recv == 2) ? p->header.command : be16_to_cpu(p->header.command);
+        char tmp[300];
+        union drbd_state m, v;
+
+        switch (cmd) {
+        case P_HAND_SHAKE:
+                INFOP("%s (protocol %u-%u)\n", cmdname(cmd),
+                        be32_to_cpu(p->handshake.protocol_min),
+                        be32_to_cpu(p->handshake.protocol_max));
+                break;
+
+        case P_BITMAP: /* don't report this */
+        case P_COMPRESSED_BITMAP: /* don't report this */
+                break;
+
+        case P_DATA:
+                INFOP("%s (sector %llus, id %s, seq %u, f %x)\n", cmdname(cmd),
+                      (unsigned long long)be64_to_cpu(p->data.sector),
+                      _dump_block_id(p->data.block_id, tmp),
+                      be32_to_cpu(p->data.seq_num),
+                      be32_to_cpu(p->data.dp_flags)
+                        );
+                break;
+
+        case P_DATA_REPLY:
+        case P_RS_DATA_REPLY:
+                INFOP("%s (sector %llus, id %s)\n", cmdname(cmd),
+                      (unsigned long long)be64_to_cpu(p->data.sector),
+                      _dump_block_id(p->data.block_id, tmp)
+                        );
+                break;
+
+        case P_RECV_ACK:
+        case P_WRITE_ACK:
+        case P_RS_WRITE_ACK:
+        case P_DISCARD_ACK:
+        case P_NEG_ACK:
+        case P_NEG_RS_DREPLY:
+                INFOP("%s (sector %llus, size %u, id %s, seq %u)\n",
+                        cmdname(cmd),
+                      (long long)be64_to_cpu(p->block_ack.sector),
+                      be32_to_cpu(p->block_ack.blksize),
+                      _dump_block_id(p->block_ack.block_id, tmp),
+                      be32_to_cpu(p->block_ack.seq_num)
+                        );
+                break;
+
+        case P_DATA_REQUEST:
+        case P_RS_DATA_REQUEST:
+                INFOP("%s (sector %llus, size %u, id %s)\n", cmdname(cmd),
+                      (long long)be64_to_cpu(p->block_req.sector),
+                      be32_to_cpu(p->block_req.blksize),
+                      _dump_block_id(p->block_req.block_id, tmp)
+                        );
+                break;
+
+        case P_BARRIER:
+        case P_BARRIER_ACK:
+                INFOP("%s (barrier %u)\n", cmdname(cmd), p->barrier.barrier);
+                break;
+
+        case P_SYNC_PARAM:
+        case P_SYNC_PARAM89:
+                INFOP("%s (rate %u, verify-alg \"%.64s\", csums-alg \"%.64s\")\n",
+                        cmdname(cmd), be32_to_cpu(p->rs_param_89.rate),
+                        p->rs_param_89.verify_alg, p->rs_param_89.csums_alg);
+                break;
+
+        case P_UUIDS:
+                INFOP("%s Curr:%016llX, Bitmap:%016llX, "
+                      "HisSt:%016llX, HisEnd:%016llX\n",
+                      cmdname(cmd),
+                      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_CURRENT]),
+                      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_BITMAP]),
+                      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_HISTORY_START]),
+                      (unsigned long long)be64_to_cpu(p->uuids.uuid[UI_HISTORY_END]));
+                break;
+
+        case P_SIZES:
+                INFOP("%s (d %lluMiB, u %lluMiB, c %lldMiB, "
+                      "max bio %x, q order %x)\n",
+                      cmdname(cmd),
+                      (long long)(be64_to_cpu(p->sizes.d_size)>>(20-9)),
+                      (long long)(be64_to_cpu(p->sizes.u_size)>>(20-9)),
+                      (long long)(be64_to_cpu(p->sizes.c_size)>>(20-9)),
+                      be32_to_cpu(p->sizes.max_segment_size),
+                      be32_to_cpu(p->sizes.queue_order_type));
+                break;
+
+        case P_STATE:
+                v.i = be32_to_cpu(p->state.state);
+                m.i = 0xffffffff;
+                dump_st(tmp, sizeof(tmp), m, v);
+                INFOP("%s (s %x {%s})\n", cmdname(cmd), v.i, tmp);
+                break;
+
+        case P_STATE_CHG_REQ:
+                m.i = be32_to_cpu(p->req_state.mask);
+                v.i = be32_to_cpu(p->req_state.val);
+                dump_st(tmp, sizeof(tmp), m, v);
+                INFOP("%s (m %x v %x {%s})\n", cmdname(cmd), m.i, v.i, tmp);
+                break;
+
+        case P_STATE_CHG_REPLY:
+                INFOP("%s (ret %x)\n", cmdname(cmd),
+                      be32_to_cpu(p->req_state_reply.retcode));
+                break;
+
+        case P_PING:
+        case P_PING_ACK:
+                /*
+                 * Dont trace pings at summary level
+                 */
+                if (trace_level < TRACE_LVL_ALL)
+                        break;
+                /* fall through... */
+        default:
+                INFOP("%s (%u)\n", cmdname(cmd), cmd);
+                break;
+        }
+}
+
+
+static int __init drbd_trace_init(void)
+{
+        int ret;
+
+        if (trace_mask & TRACE_UNPLUG) {
+                ret = register_trace_drbd_unplug(probe_drbd_unplug);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_UUID) {
+                ret = register_trace_drbd_uuid(probe_drbd_uuid);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_EE) {
+                ret = register_trace_drbd_ee(probe_drbd_ee);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_PACKET) {
+                ret = register_trace_drbd_packet(probe_drbd_packet);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_MD_IO) {
+                ret = register_trace_drbd_md_io(probe_drbd_md_io);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_EPOCH) {
+                ret = register_trace_drbd_epoch(probe_drbd_epoch);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_NL) {
+                ret = register_trace_drbd_netlink(probe_drbd_netlink);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_AL_EXT) {
+                ret = register_trace_drbd_actlog(probe_drbd_actlog);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_RQ) {
+                ret = register_trace_drbd_bio(probe_drbd_bio);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_INT_RQ) {
+                ret = register_trace_drbd_req(probe_drbd_req);
+                WARN_ON(ret);
+        }
+        if (trace_mask & TRACE_RESYNC) {
+                ret = register_trace__drbd_resync(probe_drbd_resync);
+                WARN_ON(ret);
+        }
+        return 0;
+}
+
+module_init(drbd_trace_init);
+
+static void __exit drbd_trace_exit(void)
+{
+        if (trace_mask & TRACE_UNPLUG)
+                unregister_trace_drbd_unplug(probe_drbd_unplug);
+        if (trace_mask & TRACE_UUID)
+                unregister_trace_drbd_uuid(probe_drbd_uuid);
+        if (trace_mask & TRACE_EE)
+                unregister_trace_drbd_ee(probe_drbd_ee);
+        if (trace_mask & TRACE_PACKET)
+                unregister_trace_drbd_packet(probe_drbd_packet);
+        if (trace_mask & TRACE_MD_IO)
+                unregister_trace_drbd_md_io(probe_drbd_md_io);
+        if (trace_mask & TRACE_EPOCH)
+                unregister_trace_drbd_epoch(probe_drbd_epoch);
+        if (trace_mask & TRACE_NL)
+                unregister_trace_drbd_netlink(probe_drbd_netlink);
+        if (trace_mask & TRACE_AL_EXT)
+                unregister_trace_drbd_actlog(probe_drbd_actlog);
+        if (trace_mask & TRACE_RQ)
+                unregister_trace_drbd_bio(probe_drbd_bio);
+        if (trace_mask & TRACE_INT_RQ)
+                unregister_trace_drbd_req(probe_drbd_req);
+        if (trace_mask & TRACE_RESYNC)
+                unregister_trace__drbd_resync(probe_drbd_resync);
+
+        tracepoint_synchronize_unregister();
+}
+
+module_exit(drbd_trace_exit);
diff --git a/drivers/block/drbd/drbd_tracing.h b/drivers/block/drbd/drbd_tracing.h
new file mode 100644
index 000000000000..c4531a137f65
--- /dev/null
+++ b/drivers/block/drbd/drbd_tracing.h
@@ -0,0 +1,87 @@
+/*
+   drbd_tracing.h
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2003-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 2003-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2003-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#ifndef DRBD_TRACING_H
+#define DRBD_TRACING_H
+
+#include <linux/tracepoint.h>
+#include "drbd_int.h"
+#include "drbd_req.h"
+
+enum {
+        TRACE_LVL_ALWAYS = 0,
+        TRACE_LVL_SUMMARY,
+        TRACE_LVL_METRICS,
+        TRACE_LVL_ALL,
+        TRACE_LVL_MAX
+};
+
+DECLARE_TRACE(drbd_unplug,
+        TP_PROTO(struct drbd_conf *mdev, char* msg),
+        TP_ARGS(mdev, msg));
+
+DECLARE_TRACE(drbd_uuid,
+        TP_PROTO(struct drbd_conf *mdev, enum drbd_uuid_index index),
+        TP_ARGS(mdev, index));
+
+DECLARE_TRACE(drbd_ee,
+        TP_PROTO(struct drbd_conf *mdev, struct drbd_epoch_entry *e, char* msg),
+        TP_ARGS(mdev, e, msg));
+
+DECLARE_TRACE(drbd_md_io,
+        TP_PROTO(struct drbd_conf *mdev, int rw, struct drbd_backing_dev *bdev),
+        TP_ARGS(mdev, rw, bdev));
+
+DECLARE_TRACE(drbd_epoch,
+        TP_PROTO(struct drbd_conf *mdev, struct drbd_epoch *epoch, enum epoch_event ev),
+        TP_ARGS(mdev, epoch, ev));
+
+DECLARE_TRACE(drbd_netlink,
+        TP_PROTO(void *data, int is_req),
+        TP_ARGS(data, is_req));
+
+DECLARE_TRACE(drbd_actlog,
+        TP_PROTO(struct drbd_conf *mdev, sector_t sector, char* msg),
+        TP_ARGS(mdev, sector, msg));
+
+DECLARE_TRACE(drbd_bio,
+        TP_PROTO(struct drbd_conf *mdev, const char *pfx, struct bio *bio, int complete,
+                 struct drbd_request *r),
+        TP_ARGS(mdev, pfx, bio, complete, r));
+
+DECLARE_TRACE(drbd_req,
+        TP_PROTO(struct drbd_request *req, enum drbd_req_event what, char *msg),
+              TP_ARGS(req, what, msg));
+
+DECLARE_TRACE(drbd_packet,
+        TP_PROTO(struct drbd_conf *mdev, struct socket *sock,
+                 int recv, union p_polymorph *p, char *file, int line),
+        TP_ARGS(mdev, sock, recv, p, file, line));
+
+DECLARE_TRACE(_drbd_resync,
+        TP_PROTO(struct drbd_conf *mdev, int level, const char *fmt, va_list args),
+        TP_ARGS(mdev, level, fmt, args));
+
+#endif
diff --git a/drivers/block/drbd/drbd_vli.h b/drivers/block/drbd/drbd_vli.h
new file mode 100644
index 000000000000..fc824006e721
--- /dev/null
+++ b/drivers/block/drbd/drbd_vli.h
@@ -0,0 +1,351 @@
+/*
+-*- linux-c -*-
+   drbd_receiver.c
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#ifndef _DRBD_VLI_H
+#define _DRBD_VLI_H
+
+/*
+ * At a granularity of 4KiB storage represented per bit,
+ * and stroage sizes of several TiB,
+ * and possibly small-bandwidth replication,
+ * the bitmap transfer time can take much too long,
+ * if transmitted in plain text.
+ *
+ * We try to reduce the transfered bitmap information
+ * by encoding runlengths of bit polarity.
+ *
+ * We never actually need to encode a "zero" (runlengths are positive).
+ * But then we have to store the value of the first bit.
+ * The first bit of information thus shall encode if the first runlength
+ * gives the number of set or unset bits.
+ *
+ * We assume that large areas are either completely set or unset,
+ * which gives good compression with any runlength method,
+ * even when encoding the runlength as fixed size 32bit/64bit integers.
+ *
+ * Still, there may be areas where the polarity flips every few bits,
+ * and encoding the runlength sequence of those areas with fix size
+ * integers would be much worse than plaintext.
+ *
+ * We want to encode small runlength values with minimum code length,
+ * while still being able to encode a Huge run of all zeros.
+ *
+ * Thus we need a Variable Length Integer encoding, VLI.
+ *
+ * For some cases, we produce more code bits than plaintext input.
+ * We need to send incompressible chunks as plaintext, skip over them
+ * and then see if the next chunk compresses better.
+ *
+ * We don't care too much about "excellent" compression ratio for large
+ * runlengths (all set/all clear): whether we achieve a factor of 100
+ * or 1000 is not that much of an issue.
+ * We do not want to waste too much on short runlengths in the "noisy"
+ * parts of the bitmap, though.
+ *
+ * There are endless variants of VLI, we experimented with:
+ *  * simple byte-based
+ *  * various bit based with different code word length.
+ *
+ * To avoid yet an other configuration parameter (choice of bitmap compression
+ * algorithm) which was difficult to explain and tune, we just chose the one
+ * variant that turned out best in all test cases.
+ * Based on real world usage patterns, with device sizes ranging from a few GiB
+ * to several TiB, file server/mailserver/webserver/mysql/postgress,
+ * mostly idle to really busy, the all time winner (though sometimes only
+ * marginally better) is:
+ */
+
+/*
+ * encoding is "visualised" as
+ * __little endian__ bitstream, least significant bit first (left most)
+ *
+ * this particular encoding is chosen so that the prefix code
+ * starts as unary encoding the level, then modified so that
+ * 10 levels can be described in 8bit, with minimal overhead
+ * for the smaller levels.
+ *
+ * Number of data bits follow fibonacci sequence, with the exception of the
+ * last level (+1 data bit, so it makes 64bit total).  The only worse code when
+ * encoding bit polarity runlength is 1 plain bits => 2 code bits.
+prefix    data bits                                    max val  Nº data bits
+0 x                                                         0x2            1
+10 x                                                        0x4            1
+110 xx                                                      0x8            2
+1110 xxx                                                   0x10            3
+11110 xxx xx                                               0x30            5
+111110 xx xxxxxx                                          0x130            8
+11111100  xxxxxxxx xxxxx                                 0x2130           13
+11111110  xxxxxxxx xxxxxxxx xxxxx                      0x202130           21
+11111101  xxxxxxxx xxxxxxxx xxxxxxxx  xxxxxxxx xx   0x400202130           34
+11111111  xxxxxxxx xxxxxxxx xxxxxxxx  xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx 56
+ * maximum encodable value: 0x100000400202130 == 2**56 + some */
+
+/* compression "table":
+ transmitted   x                                0.29
+ as plaintext x                                  ........................
+             x                                   ........................
+            x                                    ........................
+           x    0.59                         0.21........................
+          x      ........................................................
+         x       .. c ...................................................
+        x    0.44.. o ...................................................
+       x .......... d ...................................................
+      x  .......... e ...................................................
+     X.............   ...................................................
+    x.............. b ...................................................
+2.0x............... i ...................................................
+ #X................ t ...................................................
+ #................. s ...........................  plain bits  ..........
+-+-----------------------------------------------------------------------
+ 1             16              32                              64
+*/
+
+/* LEVEL: (total bits, prefix bits, prefix value),
+ * sorted ascending by number of total bits.
+ * The rest of the code table is calculated at compiletime from this. */
+
+/* fibonacci data 1, 1, ... */
+#define VLI_L_1_1() do { \
+        LEVEL( 2, 1, 0x00); \
+        LEVEL( 3, 2, 0x01); \
+        LEVEL( 5, 3, 0x03); \
+        LEVEL( 7, 4, 0x07); \
+        LEVEL(10, 5, 0x0f); \
+        LEVEL(14, 6, 0x1f); \
+        LEVEL(21, 8, 0x3f); \
+        LEVEL(29, 8, 0x7f); \
+        LEVEL(42, 8, 0xbf); \
+        LEVEL(64, 8, 0xff); \
+        } while (0)
+
+/* finds a suitable level to decode the least significant part of in.
+ * returns number of bits consumed.
+ *
+ * BUG() for bad input, as that would mean a buggy code table. */
+static inline int vli_decode_bits(u64 *out, const u64 in)
+{
+        u64 adj = 1;
+
+#define LEVEL(t,b,v)                                    \
+        do {                                            \
+                if ((in & ((1 << b) -1)) == v) {        \
+                        *out = ((in & ((~0ULL) >> (64-t))) >> b) + adj; \
+                        return t;                       \
+                }                                       \
+                adj += 1ULL << (t - b);                 \
+        } while (0)
+
+        VLI_L_1_1();
+
+        /* NOT REACHED, if VLI_LEVELS code table is defined properly */
+        BUG();
+#undef LEVEL
+}
+
+/* return number of code bits needed,
+ * or negative error number */
+static inline int __vli_encode_bits(u64 *out, const u64 in)
+{
+        u64 max = 0;
+        u64 adj = 1;
+
+        if (in == 0)
+                return -EINVAL;
+
+#define LEVEL(t,b,v) do {               \
+                max += 1ULL << (t - b); \
+                if (in <= max) {        \
+                        if (out)        \
+                                *out = ((in - adj) << b) | v;   \
+                        return t;       \
+                }                       \
+                adj = max + 1;          \
+        } while (0)
+
+        VLI_L_1_1();
+
+        return -EOVERFLOW;
+#undef LEVEL
+}
+
+#undef VLI_L_1_1
+
+/* code from here down is independend of actually used bit code */
+
+/*
+ * Code length is determined by some unique (e.g. unary) prefix.
+ * This encodes arbitrary bit length, not whole bytes: we have a bit-stream,
+ * not a byte stream.
+ */
+
+/* for the bitstream, we need a cursor */
+struct bitstream_cursor {
+        /* the current byte */
+        u8 *b;
+        /* the current bit within *b, nomalized: 0..7 */
+        unsigned int bit;
+};
+
+/* initialize cursor to point to first bit of stream */
+static inline void bitstream_cursor_reset(struct bitstream_cursor *cur, void *s)
+{
+        cur->b = s;
+        cur->bit = 0;
+}
+
+/* advance cursor by that many bits; maximum expected input value: 64,
+ * but depending on VLI implementation, it may be more. */
+static inline void bitstream_cursor_advance(struct bitstream_cursor *cur, unsigned int bits)
+{
+        bits += cur->bit;
+        cur->b = cur->b + (bits >> 3);
+        cur->bit = bits & 7;
+}
+
+/* the bitstream itself knows its length */
+struct bitstream {
+        struct bitstream_cursor cur;
+        unsigned char *buf;
+        size_t buf_len;         /* in bytes */
+
+        /* for input stream:
+         * number of trailing 0 bits for padding
+         * total number of valid bits in stream: buf_len * 8 - pad_bits */
+        unsigned int pad_bits;
+};
+
+static inline void bitstream_init(struct bitstream *bs, void *s, size_t len, unsigned int pad_bits)
+{
+        bs->buf = s;
+        bs->buf_len = len;
+        bs->pad_bits = pad_bits;
+        bitstream_cursor_reset(&bs->cur, bs->buf);
+}
+
+static inline void bitstream_rewind(struct bitstream *bs)
+{
+        bitstream_cursor_reset(&bs->cur, bs->buf);
+        memset(bs->buf, 0, bs->buf_len);
+}
+
+/* Put (at most 64) least significant bits of val into bitstream, and advance cursor.
+ * Ignores "pad_bits".
+ * Returns zero if bits == 0 (nothing to do).
+ * Returns number of bits used if successful.
+ *
+ * If there is not enough room left in bitstream,
+ * leaves bitstream unchanged and returns -ENOBUFS.
+ */
+static inline int bitstream_put_bits(struct bitstream *bs, u64 val, const unsigned int bits)
+{
+        unsigned char *b = bs->cur.b;
+        unsigned int tmp;
+
+        if (bits == 0)
+                return 0;
+
+        if ((bs->cur.b + ((bs->cur.bit + bits -1) >> 3)) - bs->buf >= bs->buf_len)
+                return -ENOBUFS;
+
+        /* paranoia: strip off hi bits; they should not be set anyways. */
+        if (bits < 64)
+                val &= ~0ULL >> (64 - bits);
+
+        *b++ |= (val & 0xff) << bs->cur.bit;
+
+        for (tmp = 8 - bs->cur.bit; tmp < bits; tmp += 8)
+                *b++ |= (val >> tmp) & 0xff;
+
+        bitstream_cursor_advance(&bs->cur, bits);
+        return bits;
+}
+
+/* Fetch (at most 64) bits from bitstream into *out, and advance cursor.
+ *
+ * If more than 64 bits are requested, returns -EINVAL and leave *out unchanged.
+ *
+ * If there are less than the requested number of valid bits left in the
+ * bitstream, still fetches all available bits.
+ *
+ * Returns number of actually fetched bits.
+ */
+static inline int bitstream_get_bits(struct bitstream *bs, u64 *out, int bits)
+{
+        u64 val;
+        unsigned int n;
+
+        if (bits > 64)
+                return -EINVAL;
+
+        if (bs->cur.b + ((bs->cur.bit + bs->pad_bits + bits -1) >> 3) - bs->buf >= bs->buf_len)
+                bits = ((bs->buf_len - (bs->cur.b - bs->buf)) << 3)
+                        - bs->cur.bit - bs->pad_bits;
+
+        if (bits == 0) {
+                *out = 0;
+                return 0;
+        }
+
+        /* get the high bits */
+        val = 0;
+        n = (bs->cur.bit + bits + 7) >> 3;
+        /* n may be at most 9, if cur.bit + bits > 64 */
+        /* which means this copies at most 8 byte */
+        if (n) {
+                memcpy(&val, bs->cur.b+1, n - 1);
+                val = le64_to_cpu(val) << (8 - bs->cur.bit);
+        }
+
+        /* we still need the low bits */
+        val |= bs->cur.b[0] >> bs->cur.bit;
+
+        /* and mask out bits we don't want */
+        val &= ~0ULL >> (64 - bits);
+
+        bitstream_cursor_advance(&bs->cur, bits);
+        *out = val;
+
+        return bits;
+}
+
+/* encodes @in as vli into @bs;
+
+ * return values
+ *  > 0: number of bits successfully stored in bitstream
+ * -ENOBUFS @bs is full
+ * -EINVAL input zero (invalid)
+ * -EOVERFLOW input too large for this vli code (invalid)
+ */
+static inline int vli_encode_bits(struct bitstream *bs, u64 in)
+{
+        u64 code = code;
+        int bits = __vli_encode_bits(&code, in);
+
+        if (bits <= 0)
+                return bits;
+
+        return bitstream_put_bits(bs, code, bits);
+}
+
+#endif
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
new file mode 100644
index 000000000000..212e9545e634
--- /dev/null
+++ b/drivers/block/drbd/drbd_worker.c
@@ -0,0 +1,1529 @@
+/*
+   drbd_worker.c
+
+   This file is part of DRBD by Philipp Reisner and Lars Ellenberg.
+
+   Copyright (C) 2001-2008, LINBIT Information Technologies GmbH.
+   Copyright (C) 1999-2008, Philipp Reisner <philipp.reisner@linbit.com>.
+   Copyright (C) 2002-2008, Lars Ellenberg <lars.ellenberg@linbit.com>.
+
+   drbd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   drbd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with drbd; see the file COPYING.  If not, write to
+   the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+ */
+
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/drbd.h>
+#include <linux/sched.h>
+#include <linux/smp_lock.h>
+#include <linux/wait.h>
+#include <linux/mm.h>
+#include <linux/memcontrol.h>
+#include <linux/mm_inline.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/scatterlist.h>
+
+#include "drbd_int.h"
+#include "drbd_req.h"
+#include "drbd_tracing.h"
+
+#define SLEEP_TIME (HZ/10)
+
+static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int cancel);
+
+
+
+/* defined here:
+   drbd_md_io_complete
+   drbd_endio_write_sec
+   drbd_endio_read_sec
+   drbd_endio_pri
+
+ * more endio handlers:
+   atodb_endio in drbd_actlog.c
+   drbd_bm_async_io_complete in drbd_bitmap.c
+
+ * For all these callbacks, note the following:
+ * The callbacks will be called in irq context by the IDE drivers,
+ * and in Softirqs/Tasklets/BH context by the SCSI drivers.
+ * Try to get the locking right :)
+ *
+ */
+
+
+/* About the global_state_lock
+   Each state transition on an device holds a read lock. In case we have
+   to evaluate the sync after dependencies, we grab a write lock, because
+   we need stable states on all devices for that.  */
+rwlock_t global_state_lock;
+
+/* used for synchronous meta data and bitmap IO
+ * submitted by drbd_md_sync_page_io()
+ */
+void drbd_md_io_complete(struct bio *bio, int error)
+{
+        struct drbd_md_io *md_io;
+
+        md_io = (struct drbd_md_io *)bio->bi_private;
+        md_io->error = error;
+
+        trace_drbd_bio(md_io->mdev, "Md", bio, 1, NULL);
+
+        complete(&md_io->event);
+}
+
+/* reads on behalf of the partner,
+ * "submitted" by the receiver
+ */
+void drbd_endio_read_sec(struct bio *bio, int error) __releases(local)
+{
+        unsigned long flags = 0;
+        struct drbd_epoch_entry *e = NULL;
+        struct drbd_conf *mdev;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+        e = bio->bi_private;
+        mdev = e->mdev;
+
+        if (error)
+                dev_warn(DEV, "read: error=%d s=%llus\n", error,
+                                (unsigned long long)e->sector);
+        if (!error && !uptodate) {
+                dev_warn(DEV, "read: setting error to -EIO s=%llus\n",
+                                (unsigned long long)e->sector);
+                /* strange behavior of some lower level drivers...
+                 * fail the request by clearing the uptodate flag,
+                 * but do not return any error?! */
+                error = -EIO;
+        }
+
+        D_ASSERT(e->block_id != ID_VACANT);
+
+        trace_drbd_bio(mdev, "Sec", bio, 1, NULL);
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        mdev->read_cnt += e->size >> 9;
+        list_del(&e->w.list);
+        if (list_empty(&mdev->read_ee))
+                wake_up(&mdev->ee_wait);
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        drbd_chk_io_error(mdev, error, FALSE);
+        drbd_queue_work(&mdev->data.work, &e->w);
+        put_ldev(mdev);
+
+        trace_drbd_ee(mdev, e, "read completed");
+}
+
+/* writes on behalf of the partner, or resync writes,
+ * "submitted" by the receiver.
+ */
+void drbd_endio_write_sec(struct bio *bio, int error) __releases(local)
+{
+        unsigned long flags = 0;
+        struct drbd_epoch_entry *e = NULL;
+        struct drbd_conf *mdev;
+        sector_t e_sector;
+        int do_wake;
+        int is_syncer_req;
+        int do_al_complete_io;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+        int is_barrier = bio_rw_flagged(bio, BIO_RW_BARRIER);
+
+        e = bio->bi_private;
+        mdev = e->mdev;
+
+        if (error)
+                dev_warn(DEV, "write: error=%d s=%llus\n", error,
+                                (unsigned long long)e->sector);
+        if (!error && !uptodate) {
+                dev_warn(DEV, "write: setting error to -EIO s=%llus\n",
+                                (unsigned long long)e->sector);
+                /* strange behavior of some lower level drivers...
+                 * fail the request by clearing the uptodate flag,
+                 * but do not return any error?! */
+                error = -EIO;
+        }
+
+        /* error == -ENOTSUPP would be a better test,
+         * alas it is not reliable */
+        if (error && is_barrier && e->flags & EE_IS_BARRIER) {
+                drbd_bump_write_ordering(mdev, WO_bdev_flush);
+                spin_lock_irqsave(&mdev->req_lock, flags);
+                list_del(&e->w.list);
+                e->w.cb = w_e_reissue;
+                /* put_ldev actually happens below, once we come here again. */
+                __release(local);
+                spin_unlock_irqrestore(&mdev->req_lock, flags);
+                drbd_queue_work(&mdev->data.work, &e->w);
+                return;
+        }
+
+        D_ASSERT(e->block_id != ID_VACANT);
+
+        trace_drbd_bio(mdev, "Sec", bio, 1, NULL);
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        mdev->writ_cnt += e->size >> 9;
+        is_syncer_req = is_syncer_block_id(e->block_id);
+
+        /* after we moved e to done_ee,
+         * we may no longer access it,
+         * it may be freed/reused already!
+         * (as soon as we release the req_lock) */
+        e_sector = e->sector;
+        do_al_complete_io = e->flags & EE_CALL_AL_COMPLETE_IO;
+
+        list_del(&e->w.list); /* has been on active_ee or sync_ee */
+        list_add_tail(&e->w.list, &mdev->done_ee);
+
+        trace_drbd_ee(mdev, e, "write completed");
+
+        /* No hlist_del_init(&e->colision) here, we did not send the Ack yet,
+         * neither did we wake possibly waiting conflicting requests.
+         * done from "drbd_process_done_ee" within the appropriate w.cb
+         * (e_end_block/e_end_resync_block) or from _drbd_clear_done_ee */
+
+        do_wake = is_syncer_req
+                ? list_empty(&mdev->sync_ee)
+                : list_empty(&mdev->active_ee);
+
+        if (error)
+                __drbd_chk_io_error(mdev, FALSE);
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        if (is_syncer_req)
+                drbd_rs_complete_io(mdev, e_sector);
+
+        if (do_wake)
+                wake_up(&mdev->ee_wait);
+
+        if (do_al_complete_io)
+                drbd_al_complete_io(mdev, e_sector);
+
+        wake_asender(mdev);
+        put_ldev(mdev);
+
+}
+
+/* read, readA or write requests on R_PRIMARY coming from drbd_make_request
+ */
+void drbd_endio_pri(struct bio *bio, int error)
+{
+        unsigned long flags;
+        struct drbd_request *req = bio->bi_private;
+        struct drbd_conf *mdev = req->mdev;
+        struct bio_and_error m;
+        enum drbd_req_event what;
+        int uptodate = bio_flagged(bio, BIO_UPTODATE);
+
+        if (error)
+                dev_warn(DEV, "p %s: error=%d\n",
+                         bio_data_dir(bio) == WRITE ? "write" : "read", error);
+        if (!error && !uptodate) {
+                dev_warn(DEV, "p %s: setting error to -EIO\n",
+                         bio_data_dir(bio) == WRITE ? "write" : "read");
+                /* strange behavior of some lower level drivers...
+                 * fail the request by clearing the uptodate flag,
+                 * but do not return any error?! */
+                error = -EIO;
+        }
+
+        trace_drbd_bio(mdev, "Pri", bio, 1, NULL);
+
+        /* to avoid recursion in __req_mod */
+        if (unlikely(error)) {
+                what = (bio_data_dir(bio) == WRITE)
+                        ? write_completed_with_error
+                        : (bio_rw(bio) == READA)
+                          ? read_completed_with_error
+                          : read_ahead_completed_with_error;
+        } else
+                what = completed_ok;
+
+        bio_put(req->private_bio);
+        req->private_bio = ERR_PTR(error);
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+        __req_mod(req, what, &m);
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        if (m.bio)
+                complete_master_bio(mdev, &m);
+}
+
+int w_io_error(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_request *req = container_of(w, struct drbd_request, w);
+
+        /* NOTE: mdev->ldev can be NULL by the time we get here! */
+        /* D_ASSERT(mdev->ldev->dc.on_io_error != EP_PASS_ON); */
+
+        /* the only way this callback is scheduled is from _req_may_be_done,
+         * when it is done and had a local write error, see comments there */
+        drbd_req_free(req);
+
+        return TRUE;
+}
+
+int w_read_retry_remote(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_request *req = container_of(w, struct drbd_request, w);
+
+        /* We should not detach for read io-error,
+         * but try to WRITE the P_DATA_REPLY to the failed location,
+         * to give the disk the chance to relocate that block */
+
+        spin_lock_irq(&mdev->req_lock);
+        if (cancel ||
+            mdev->state.conn < C_CONNECTED ||
+            mdev->state.pdsk <= D_INCONSISTENT) {
+                _req_mod(req, send_canceled);
+                spin_unlock_irq(&mdev->req_lock);
+                dev_alert(DEV, "WE ARE LOST. Local IO failure, no peer.\n");
+                return 1;
+        }
+        spin_unlock_irq(&mdev->req_lock);
+
+        return w_send_read_req(mdev, w, 0);
+}
+
+int w_resync_inactive(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        ERR_IF(cancel) return 1;
+        dev_err(DEV, "resync inactive, but callback triggered??\n");
+        return 1; /* Simply ignore this! */
+}
+
+void drbd_csum(struct drbd_conf *mdev, struct crypto_hash *tfm, struct bio *bio, void *digest)
+{
+        struct hash_desc desc;
+        struct scatterlist sg;
+        struct bio_vec *bvec;
+        int i;
+
+        desc.tfm = tfm;
+        desc.flags = 0;
+
+        sg_init_table(&sg, 1);
+        crypto_hash_init(&desc);
+
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                sg_set_page(&sg, bvec->bv_page, bvec->bv_len, bvec->bv_offset);
+                crypto_hash_update(&desc, &sg, sg.length);
+        }
+        crypto_hash_final(&desc, digest);
+}
+
+static int w_e_send_csum(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        int digest_size;
+        void *digest;
+        int ok;
+
+        D_ASSERT(e->block_id == DRBD_MAGIC + 0xbeef);
+
+        if (unlikely(cancel)) {
+                drbd_free_ee(mdev, e);
+                return 1;
+        }
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                digest_size = crypto_hash_digestsize(mdev->csums_tfm);
+                digest = kmalloc(digest_size, GFP_NOIO);
+                if (digest) {
+                        drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+
+                        inc_rs_pending(mdev);
+                        ok = drbd_send_drequest_csum(mdev,
+                                                     e->sector,
+                                                     e->size,
+                                                     digest,
+                                                     digest_size,
+                                                     P_CSUM_RS_REQUEST);
+                        kfree(digest);
+                } else {
+                        dev_err(DEV, "kmalloc() of digest failed.\n");
+                        ok = 0;
+                }
+        } else
+                ok = 1;
+
+        drbd_free_ee(mdev, e);
+
+        if (unlikely(!ok))
+                dev_err(DEV, "drbd_send_drequest(..., csum) failed\n");
+        return ok;
+}
+
+#define GFP_TRY (__GFP_HIGHMEM | __GFP_NOWARN)
+
+static int read_for_csum(struct drbd_conf *mdev, sector_t sector, int size)
+{
+        struct drbd_epoch_entry *e;
+
+        if (!get_ldev(mdev))
+                return 0;
+
+        /* GFP_TRY, because if there is no memory available right now, this may
+         * be rescheduled for later. It is "only" background resync, after all. */
+        e = drbd_alloc_ee(mdev, DRBD_MAGIC+0xbeef, sector, size, GFP_TRY);
+        if (!e) {
+                put_ldev(mdev);
+                return 2;
+        }
+
+        spin_lock_irq(&mdev->req_lock);
+        list_add(&e->w.list, &mdev->read_ee);
+        spin_unlock_irq(&mdev->req_lock);
+
+        e->private_bio->bi_end_io = drbd_endio_read_sec;
+        e->private_bio->bi_rw = READ;
+        e->w.cb = w_e_send_csum;
+
+        mdev->read_cnt += size >> 9;
+        drbd_generic_make_request(mdev, DRBD_FAULT_RS_RD, e->private_bio);
+
+        return 1;
+}
+
+void resync_timer_fn(unsigned long data)
+{
+        unsigned long flags;
+        struct drbd_conf *mdev = (struct drbd_conf *) data;
+        int queue;
+
+        spin_lock_irqsave(&mdev->req_lock, flags);
+
+        if (likely(!test_and_clear_bit(STOP_SYNC_TIMER, &mdev->flags))) {
+                queue = 1;
+                if (mdev->state.conn == C_VERIFY_S)
+                        mdev->resync_work.cb = w_make_ov_request;
+                else
+                        mdev->resync_work.cb = w_make_resync_request;
+        } else {
+                queue = 0;
+                mdev->resync_work.cb = w_resync_inactive;
+        }
+
+        spin_unlock_irqrestore(&mdev->req_lock, flags);
+
+        /* harmless race: list_empty outside data.work.q_lock */
+        if (list_empty(&mdev->resync_work.list) && queue)
+                drbd_queue_work(&mdev->data.work, &mdev->resync_work);
+}
+
+int w_make_resync_request(struct drbd_conf *mdev,
+                struct drbd_work *w, int cancel)
+{
+        unsigned long bit;
+        sector_t sector;
+        const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+        int max_segment_size = queue_max_segment_size(mdev->rq_queue);
+        int number, i, size, pe, mx;
+        int align, queued, sndbuf;
+
+        if (unlikely(cancel))
+                return 1;
+
+        if (unlikely(mdev->state.conn < C_CONNECTED)) {
+                dev_err(DEV, "Confused in w_make_resync_request()! cstate < Connected");
+                return 0;
+        }
+
+        if (mdev->state.conn != C_SYNC_TARGET)
+                dev_err(DEV, "%s in w_make_resync_request\n",
+                        drbd_conn_str(mdev->state.conn));
+
+        if (!get_ldev(mdev)) {
+                /* Since we only need to access mdev->rsync a
+                   get_ldev_if_state(mdev,D_FAILED) would be sufficient, but
+                   to continue resync with a broken disk makes no sense at
+                   all */
+                dev_err(DEV, "Disk broke down during resync!\n");
+                mdev->resync_work.cb = w_resync_inactive;
+                return 1;
+        }
+
+        number = SLEEP_TIME * mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
+        pe = atomic_read(&mdev->rs_pending_cnt);
+
+        mutex_lock(&mdev->data.mutex);
+        if (mdev->data.socket)
+                mx = mdev->data.socket->sk->sk_rcvbuf / sizeof(struct p_block_req);
+        else
+                mx = 1;
+        mutex_unlock(&mdev->data.mutex);
+
+        /* For resync rates >160MB/sec, allow more pending RS requests */
+        if (number > mx)
+                mx = number;
+
+        /* Limit the number of pending RS requests to no more than the peer's receive buffer */
+        if ((pe + number) > mx) {
+                number = mx - pe;
+        }
+
+        for (i = 0; i < number; i++) {
+                /* Stop generating RS requests, when half of the send buffer is filled */
+                mutex_lock(&mdev->data.mutex);
+                if (mdev->data.socket) {
+                        queued = mdev->data.socket->sk->sk_wmem_queued;
+                        sndbuf = mdev->data.socket->sk->sk_sndbuf;
+                } else {
+                        queued = 1;
+                        sndbuf = 0;
+                }
+                mutex_unlock(&mdev->data.mutex);
+                if (queued > sndbuf / 2)
+                        goto requeue;
+
+next_sector:
+                size = BM_BLOCK_SIZE;
+                bit  = drbd_bm_find_next(mdev, mdev->bm_resync_fo);
+
+                if (bit == -1UL) {
+                        mdev->bm_resync_fo = drbd_bm_bits(mdev);
+                        mdev->resync_work.cb = w_resync_inactive;
+                        put_ldev(mdev);
+                        return 1;
+                }
+
+                sector = BM_BIT_TO_SECT(bit);
+
+                if (drbd_try_rs_begin_io(mdev, sector)) {
+                        mdev->bm_resync_fo = bit;
+                        goto requeue;
+                }
+                mdev->bm_resync_fo = bit + 1;
+
+                if (unlikely(drbd_bm_test_bit(mdev, bit) == 0)) {
+                        drbd_rs_complete_io(mdev, sector);
+                        goto next_sector;
+                }
+
+#if DRBD_MAX_SEGMENT_SIZE > BM_BLOCK_SIZE
+                /* try to find some adjacent bits.
+                 * we stop if we have already the maximum req size.
+                 *
+                 * Additionally always align bigger requests, in order to
+                 * be prepared for all stripe sizes of software RAIDs.
+                 *
+                 * we _do_ care about the agreed-upon q->max_segment_size
+                 * here, as splitting up the requests on the other side is more
+                 * difficult.  the consequence is, that on lvm and md and other
+                 * "indirect" devices, this is dead code, since
+                 * q->max_segment_size will be PAGE_SIZE.
+                 */
+                align = 1;
+                for (;;) {
+                        if (size + BM_BLOCK_SIZE > max_segment_size)
+                                break;
+
+                        /* Be always aligned */
+                        if (sector & ((1<<(align+3))-1))
+                                break;
+
+                        /* do not cross extent boundaries */
+                        if (((bit+1) & BM_BLOCKS_PER_BM_EXT_MASK) == 0)
+                                break;
+                        /* now, is it actually dirty, after all?
+                         * caution, drbd_bm_test_bit is tri-state for some
+                         * obscure reason; ( b == 0 ) would get the out-of-band
+                         * only accidentally right because of the "oddly sized"
+                         * adjustment below */
+                        if (drbd_bm_test_bit(mdev, bit+1) != 1)
+                                break;
+                        bit++;
+                        size += BM_BLOCK_SIZE;
+                        if ((BM_BLOCK_SIZE << align) <= size)
+                                align++;
+                        i++;
+                }
+                /* if we merged some,
+                 * reset the offset to start the next drbd_bm_find_next from */
+                if (size > BM_BLOCK_SIZE)
+                        mdev->bm_resync_fo = bit + 1;
+#endif
+
+                /* adjust very last sectors, in case we are oddly sized */
+                if (sector + (size>>9) > capacity)
+                        size = (capacity-sector)<<9;
+                if (mdev->agreed_pro_version >= 89 && mdev->csums_tfm) {
+                        switch (read_for_csum(mdev, sector, size)) {
+                        case 0: /* Disk failure*/
+                                put_ldev(mdev);
+                                return 0;
+                        case 2: /* Allocation failed */
+                                drbd_rs_complete_io(mdev, sector);
+                                mdev->bm_resync_fo = BM_SECT_TO_BIT(sector);
+                                goto requeue;
+                        /* case 1: everything ok */
+                        }
+                } else {
+                        inc_rs_pending(mdev);
+                        if (!drbd_send_drequest(mdev, P_RS_DATA_REQUEST,
+                                               sector, size, ID_SYNCER)) {
+                                dev_err(DEV, "drbd_send_drequest() failed, aborting...\n");
+                                dec_rs_pending(mdev);
+                                put_ldev(mdev);
+                                return 0;
+                        }
+                }
+        }
+
+        if (mdev->bm_resync_fo >= drbd_bm_bits(mdev)) {
+                /* last syncer _request_ was sent,
+                 * but the P_RS_DATA_REPLY not yet received.  sync will end (and
+                 * next sync group will resume), as soon as we receive the last
+                 * resync data block, and the last bit is cleared.
+                 * until then resync "work" is "inactive" ...
+                 */
+                mdev->resync_work.cb = w_resync_inactive;
+                put_ldev(mdev);
+                return 1;
+        }
+
+ requeue:
+        mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
+        put_ldev(mdev);
+        return 1;
+}
+
+static int w_make_ov_request(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        int number, i, size;
+        sector_t sector;
+        const sector_t capacity = drbd_get_capacity(mdev->this_bdev);
+
+        if (unlikely(cancel))
+                return 1;
+
+        if (unlikely(mdev->state.conn < C_CONNECTED)) {
+                dev_err(DEV, "Confused in w_make_ov_request()! cstate < Connected");
+                return 0;
+        }
+
+        number = SLEEP_TIME*mdev->sync_conf.rate / ((BM_BLOCK_SIZE/1024)*HZ);
+        if (atomic_read(&mdev->rs_pending_cnt) > number)
+                goto requeue;
+
+        number -= atomic_read(&mdev->rs_pending_cnt);
+
+        sector = mdev->ov_position;
+        for (i = 0; i < number; i++) {
+                if (sector >= capacity) {
+                        mdev->resync_work.cb = w_resync_inactive;
+                        return 1;
+                }
+
+                size = BM_BLOCK_SIZE;
+
+                if (drbd_try_rs_begin_io(mdev, sector)) {
+                        mdev->ov_position = sector;
+                        goto requeue;
+                }
+
+                if (sector + (size>>9) > capacity)
+                        size = (capacity-sector)<<9;
+
+                inc_rs_pending(mdev);
+                if (!drbd_send_ov_request(mdev, sector, size)) {
+                        dec_rs_pending(mdev);
+                        return 0;
+                }
+                sector += BM_SECT_PER_BIT;
+        }
+        mdev->ov_position = sector;
+
+ requeue:
+        mod_timer(&mdev->resync_timer, jiffies + SLEEP_TIME);
+        return 1;
+}
+
+
+int w_ov_finished(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        kfree(w);
+        ov_oos_print(mdev);
+        drbd_resync_finished(mdev);
+
+        return 1;
+}
+
+static int w_resync_finished(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        kfree(w);
+
+        drbd_resync_finished(mdev);
+
+        return 1;
+}
+
+int drbd_resync_finished(struct drbd_conf *mdev)
+{
+        unsigned long db, dt, dbdt;
+        unsigned long n_oos;
+        union drbd_state os, ns;
+        struct drbd_work *w;
+        char *khelper_cmd = NULL;
+
+        /* Remove all elements from the resync LRU. Since future actions
+         * might set bits in the (main) bitmap, then the entries in the
+         * resync LRU would be wrong. */
+        if (drbd_rs_del_all(mdev)) {
+                /* In case this is not possible now, most probably because
+                 * there are P_RS_DATA_REPLY Packets lingering on the worker's
+                 * queue (or even the read operations for those packets
+                 * is not finished by now).   Retry in 100ms. */
+
+                drbd_kick_lo(mdev);
+                __set_current_state(TASK_INTERRUPTIBLE);
+                schedule_timeout(HZ / 10);
+                w = kmalloc(sizeof(struct drbd_work), GFP_ATOMIC);
+                if (w) {
+                        w->cb = w_resync_finished;
+                        drbd_queue_work(&mdev->data.work, w);
+                        return 1;
+                }
+                dev_err(DEV, "Warn failed to drbd_rs_del_all() and to kmalloc(w).\n");
+        }
+
+        dt = (jiffies - mdev->rs_start - mdev->rs_paused) / HZ;
+        if (dt <= 0)
+                dt = 1;
+        db = mdev->rs_total;
+        dbdt = Bit2KB(db/dt);
+        mdev->rs_paused /= HZ;
+
+        if (!get_ldev(mdev))
+                goto out;
+
+        spin_lock_irq(&mdev->req_lock);
+        os = mdev->state;
+
+        /* This protects us against multiple calls (that can happen in the presence
+           of application IO), and against connectivity loss just before we arrive here. */
+        if (os.conn <= C_CONNECTED)
+                goto out_unlock;
+
+        ns = os;
+        ns.conn = C_CONNECTED;
+
+        dev_info(DEV, "%s done (total %lu sec; paused %lu sec; %lu K/sec)\n",
+             (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) ?
+             "Online verify " : "Resync",
+             dt + mdev->rs_paused, mdev->rs_paused, dbdt);
+
+        n_oos = drbd_bm_total_weight(mdev);
+
+        if (os.conn == C_VERIFY_S || os.conn == C_VERIFY_T) {
+                if (n_oos) {
+                        dev_alert(DEV, "Online verify found %lu %dk block out of sync!\n",
+                              n_oos, Bit2KB(1));
+                        khelper_cmd = "out-of-sync";
+                }
+        } else {
+                D_ASSERT((n_oos - mdev->rs_failed) == 0);
+
+                if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T)
+                        khelper_cmd = "after-resync-target";
+
+                if (mdev->csums_tfm && mdev->rs_total) {
+                        const unsigned long s = mdev->rs_same_csum;
+                        const unsigned long t = mdev->rs_total;
+                        const int ratio =
+                                (t == 0)     ? 0 :
+                        (t < 100000) ? ((s*100)/t) : (s/(t/100));
+                        dev_info(DEV, "%u %% had equal check sums, eliminated: %luK; "
+                             "transferred %luK total %luK\n",
+                             ratio,
+                             Bit2KB(mdev->rs_same_csum),
+                             Bit2KB(mdev->rs_total - mdev->rs_same_csum),
+                             Bit2KB(mdev->rs_total));
+                }
+        }
+
+        if (mdev->rs_failed) {
+                dev_info(DEV, "            %lu failed blocks\n", mdev->rs_failed);
+
+                if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
+                        ns.disk = D_INCONSISTENT;
+                        ns.pdsk = D_UP_TO_DATE;
+                } else {
+                        ns.disk = D_UP_TO_DATE;
+                        ns.pdsk = D_INCONSISTENT;
+                }
+        } else {
+                ns.disk = D_UP_TO_DATE;
+                ns.pdsk = D_UP_TO_DATE;
+
+                if (os.conn == C_SYNC_TARGET || os.conn == C_PAUSED_SYNC_T) {
+                        if (mdev->p_uuid) {
+                                int i;
+                                for (i = UI_BITMAP ; i <= UI_HISTORY_END ; i++)
+                                        _drbd_uuid_set(mdev, i, mdev->p_uuid[i]);
+                                drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_CURRENT]);
+                                _drbd_uuid_set(mdev, UI_CURRENT, mdev->p_uuid[UI_CURRENT]);
+                        } else {
+                                dev_err(DEV, "mdev->p_uuid is NULL! BUG\n");
+                        }
+                }
+
+                drbd_uuid_set_bm(mdev, 0UL);
+
+                if (mdev->p_uuid) {
+                        /* Now the two UUID sets are equal, update what we
+                         * know of the peer. */
+                        int i;
+                        for (i = UI_CURRENT ; i <= UI_HISTORY_END ; i++)
+                                mdev->p_uuid[i] = mdev->ldev->md.uuid[i];
+                }
+        }
+
+        _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+out_unlock:
+        spin_unlock_irq(&mdev->req_lock);
+        put_ldev(mdev);
+out:
+        mdev->rs_total  = 0;
+        mdev->rs_failed = 0;
+        mdev->rs_paused = 0;
+        mdev->ov_start_sector = 0;
+
+        if (test_and_clear_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags)) {
+                dev_warn(DEV, "Writing the whole bitmap, due to failed kmalloc\n");
+                drbd_queue_bitmap_io(mdev, &drbd_bm_write, NULL, "write from resync_finished");
+        }
+
+        if (khelper_cmd)
+                drbd_khelper(mdev, khelper_cmd);
+
+        return 1;
+}
+
+/* helper */
+static void move_to_net_ee_or_free(struct drbd_conf *mdev, struct drbd_epoch_entry *e)
+{
+        if (drbd_bio_has_active_page(e->private_bio)) {
+                /* This might happen if sendpage() has not finished */
+                spin_lock_irq(&mdev->req_lock);
+                list_add_tail(&e->w.list, &mdev->net_ee);
+                spin_unlock_irq(&mdev->req_lock);
+        } else
+                drbd_free_ee(mdev, e);
+}
+
+/**
+ * w_e_end_data_req() - Worker callback, to send a P_DATA_REPLY packet in response to a P_DATA_REQUEST
+ * @mdev:       DRBD device.
+ * @w:          work object.
+ * @cancel:     The connection will be closed anyways
+ */
+int w_e_end_data_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        int ok;
+
+        if (unlikely(cancel)) {
+                drbd_free_ee(mdev, e);
+                dec_unacked(mdev);
+                return 1;
+        }
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                ok = drbd_send_block(mdev, P_DATA_REPLY, e);
+        } else {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Sending NegDReply. sector=%llus.\n",
+                            (unsigned long long)e->sector);
+
+                ok = drbd_send_ack(mdev, P_NEG_DREPLY, e);
+        }
+
+        dec_unacked(mdev);
+
+        move_to_net_ee_or_free(mdev, e);
+
+        if (unlikely(!ok))
+                dev_err(DEV, "drbd_send_block() failed\n");
+        return ok;
+}
+
+/**
+ * w_e_end_rsdata_req() - Worker callback to send a P_RS_DATA_REPLY packet in response to a P_RS_DATA_REQUESTRS
+ * @mdev:       DRBD device.
+ * @w:          work object.
+ * @cancel:     The connection will be closed anyways
+ */
+int w_e_end_rsdata_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        int ok;
+
+        if (unlikely(cancel)) {
+                drbd_free_ee(mdev, e);
+                dec_unacked(mdev);
+                return 1;
+        }
+
+        if (get_ldev_if_state(mdev, D_FAILED)) {
+                drbd_rs_complete_io(mdev, e->sector);
+                put_ldev(mdev);
+        }
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                if (likely(mdev->state.pdsk >= D_INCONSISTENT)) {
+                        inc_rs_pending(mdev);
+                        ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
+                } else {
+                        if (__ratelimit(&drbd_ratelimit_state))
+                                dev_err(DEV, "Not sending RSDataReply, "
+                                    "partner DISKLESS!\n");
+                        ok = 1;
+                }
+        } else {
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Sending NegRSDReply. sector %llus.\n",
+                            (unsigned long long)e->sector);
+
+                ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+
+                /* update resync data with failure */
+                drbd_rs_failed_io(mdev, e->sector, e->size);
+        }
+
+        dec_unacked(mdev);
+
+        move_to_net_ee_or_free(mdev, e);
+
+        if (unlikely(!ok))
+                dev_err(DEV, "drbd_send_block() failed\n");
+        return ok;
+}
+
+int w_e_end_csum_rs_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        struct digest_info *di;
+        int digest_size;
+        void *digest = NULL;
+        int ok, eq = 0;
+
+        if (unlikely(cancel)) {
+                drbd_free_ee(mdev, e);
+                dec_unacked(mdev);
+                return 1;
+        }
+
+        drbd_rs_complete_io(mdev, e->sector);
+
+        di = (struct digest_info *)(unsigned long)e->block_id;
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                /* quick hack to try to avoid a race against reconfiguration.
+                 * a real fix would be much more involved,
+                 * introducing more locking mechanisms */
+                if (mdev->csums_tfm) {
+                        digest_size = crypto_hash_digestsize(mdev->csums_tfm);
+                        D_ASSERT(digest_size == di->digest_size);
+                        digest = kmalloc(digest_size, GFP_NOIO);
+                }
+                if (digest) {
+                        drbd_csum(mdev, mdev->csums_tfm, e->private_bio, digest);
+                        eq = !memcmp(digest, di->digest, digest_size);
+                        kfree(digest);
+                }
+
+                if (eq) {
+                        drbd_set_in_sync(mdev, e->sector, e->size);
+                        mdev->rs_same_csum++;
+                        ok = drbd_send_ack(mdev, P_RS_IS_IN_SYNC, e);
+                } else {
+                        inc_rs_pending(mdev);
+                        e->block_id = ID_SYNCER;
+                        ok = drbd_send_block(mdev, P_RS_DATA_REPLY, e);
+                }
+        } else {
+                ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
+        }
+
+        dec_unacked(mdev);
+
+        kfree(di);
+
+        move_to_net_ee_or_free(mdev, e);
+
+        if (unlikely(!ok))
+                dev_err(DEV, "drbd_send_block/ack() failed\n");
+        return ok;
+}
+
+int w_e_end_ov_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        int digest_size;
+        void *digest;
+        int ok = 1;
+
+        if (unlikely(cancel))
+                goto out;
+
+        if (unlikely(!drbd_bio_uptodate(e->private_bio)))
+                goto out;
+
+        digest_size = crypto_hash_digestsize(mdev->verify_tfm);
+        /* FIXME if this allocation fails, online verify will not terminate! */
+        digest = kmalloc(digest_size, GFP_NOIO);
+        if (digest) {
+                drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+                inc_rs_pending(mdev);
+                ok = drbd_send_drequest_csum(mdev, e->sector, e->size,
+                                             digest, digest_size, P_OV_REPLY);
+                if (!ok)
+                        dec_rs_pending(mdev);
+                kfree(digest);
+        }
+
+out:
+        drbd_free_ee(mdev, e);
+
+        dec_unacked(mdev);
+
+        return ok;
+}
+
+void drbd_ov_oos_found(struct drbd_conf *mdev, sector_t sector, int size)
+{
+        if (mdev->ov_last_oos_start + mdev->ov_last_oos_size == sector) {
+                mdev->ov_last_oos_size += size>>9;
+        } else {
+                mdev->ov_last_oos_start = sector;
+                mdev->ov_last_oos_size = size>>9;
+        }
+        drbd_set_out_of_sync(mdev, sector, size);
+        set_bit(WRITE_BM_AFTER_RESYNC, &mdev->flags);
+}
+
+int w_e_end_ov_reply(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_epoch_entry *e = container_of(w, struct drbd_epoch_entry, w);
+        struct digest_info *di;
+        int digest_size;
+        void *digest;
+        int ok, eq = 0;
+
+        if (unlikely(cancel)) {
+                drbd_free_ee(mdev, e);
+                dec_unacked(mdev);
+                return 1;
+        }
+
+        /* after "cancel", because after drbd_disconnect/drbd_rs_cancel_all
+         * the resync lru has been cleaned up already */
+        drbd_rs_complete_io(mdev, e->sector);
+
+        di = (struct digest_info *)(unsigned long)e->block_id;
+
+        if (likely(drbd_bio_uptodate(e->private_bio))) {
+                digest_size = crypto_hash_digestsize(mdev->verify_tfm);
+                digest = kmalloc(digest_size, GFP_NOIO);
+                if (digest) {
+                        drbd_csum(mdev, mdev->verify_tfm, e->private_bio, digest);
+
+                        D_ASSERT(digest_size == di->digest_size);
+                        eq = !memcmp(digest, di->digest, digest_size);
+                        kfree(digest);
+                }
+        } else {
+                ok = drbd_send_ack(mdev, P_NEG_RS_DREPLY, e);
+                if (__ratelimit(&drbd_ratelimit_state))
+                        dev_err(DEV, "Sending NegDReply. I guess it gets messy.\n");
+        }
+
+        dec_unacked(mdev);
+
+        kfree(di);
+
+        if (!eq)
+                drbd_ov_oos_found(mdev, e->sector, e->size);
+        else
+                ov_oos_print(mdev);
+
+        ok = drbd_send_ack_ex(mdev, P_OV_RESULT, e->sector, e->size,
+                              eq ? ID_IN_SYNC : ID_OUT_OF_SYNC);
+
+        drbd_free_ee(mdev, e);
+
+        if (--mdev->ov_left == 0) {
+                ov_oos_print(mdev);
+                drbd_resync_finished(mdev);
+        }
+
+        return ok;
+}
+
+int w_prev_work_done(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_wq_barrier *b = container_of(w, struct drbd_wq_barrier, w);
+        complete(&b->done);
+        return 1;
+}
+
+int w_send_barrier(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_tl_epoch *b = container_of(w, struct drbd_tl_epoch, w);
+        struct p_barrier *p = &mdev->data.sbuf.barrier;
+        int ok = 1;
+
+        /* really avoid racing with tl_clear.  w.cb may have been referenced
+         * just before it was reassigned and re-queued, so double check that.
+         * actually, this race was harmless, since we only try to send the
+         * barrier packet here, and otherwise do nothing with the object.
+         * but compare with the head of w_clear_epoch */
+        spin_lock_irq(&mdev->req_lock);
+        if (w->cb != w_send_barrier || mdev->state.conn < C_CONNECTED)
+                cancel = 1;
+        spin_unlock_irq(&mdev->req_lock);
+        if (cancel)
+                return 1;
+
+        if (!drbd_get_data_sock(mdev))
+                return 0;
+        p->barrier = b->br_number;
+        /* inc_ap_pending was done where this was queued.
+         * dec_ap_pending will be done in got_BarrierAck
+         * or (on connection loss) in w_clear_epoch.  */
+        ok = _drbd_send_cmd(mdev, mdev->data.socket, P_BARRIER,
+                                (struct p_header *)p, sizeof(*p), 0);
+        drbd_put_data_sock(mdev);
+
+        return ok;
+}
+
+int w_send_write_hint(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        if (cancel)
+                return 1;
+        return drbd_send_short_cmd(mdev, P_UNPLUG_REMOTE);
+}
+
+/**
+ * w_send_dblock() - Worker callback to send a P_DATA packet in order to mirror a write request
+ * @mdev:       DRBD device.
+ * @w:          work object.
+ * @cancel:     The connection will be closed anyways
+ */
+int w_send_dblock(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_request *req = container_of(w, struct drbd_request, w);
+        int ok;
+
+        if (unlikely(cancel)) {
+                req_mod(req, send_canceled);
+                return 1;
+        }
+
+        ok = drbd_send_dblock(mdev, req);
+        req_mod(req, ok ? handed_over_to_network : send_failed);
+
+        return ok;
+}
+
+/**
+ * w_send_read_req() - Worker callback to send a read request (P_DATA_REQUEST) packet
+ * @mdev:       DRBD device.
+ * @w:          work object.
+ * @cancel:     The connection will be closed anyways
+ */
+int w_send_read_req(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
+{
+        struct drbd_request *req = container_of(w, struct drbd_request, w);
+        int ok;
+
+        if (unlikely(cancel)) {
+                req_mod(req, send_canceled);
+                return 1;
+        }
+
+        ok = drbd_send_drequest(mdev, P_DATA_REQUEST, req->sector, req->size,
+                                (unsigned long)req);
+
+        if (!ok) {
+                /* ?? we set C_TIMEOUT or C_BROKEN_PIPE in drbd_send();
+                 * so this is probably redundant */
+                if (mdev->state.conn >= C_CONNECTED)
+                        drbd_force_state(mdev, NS(conn, C_NETWORK_FAILURE));
+        }
+        req_mod(req, ok ? handed_over_to_network : send_failed);
+
+        return ok;
+}
+
+static int _drbd_may_sync_now(struct drbd_conf *mdev)
+{
+        struct drbd_conf *odev = mdev;
+
+        while (1) {
+                if (odev->sync_conf.after == -1)
+                        return 1;
+                odev = minor_to_mdev(odev->sync_conf.after);
+                ERR_IF(!odev) return 1;
+                if ((odev->state.conn >= C_SYNC_SOURCE &&
+                     odev->state.conn <= C_PAUSED_SYNC_T) ||
+                    odev->state.aftr_isp || odev->state.peer_isp ||
+                    odev->state.user_isp)
+                        return 0;
+        }
+}
+
+/**
+ * _drbd_pause_after() - Pause resync on all devices that may not resync now
+ * @mdev:       DRBD device.
+ *
+ * Called from process context only (admin command and after_state_ch).
+ */
+static int _drbd_pause_after(struct drbd_conf *mdev)
+{
+        struct drbd_conf *odev;
+        int i, rv = 0;
+
+        for (i = 0; i < minor_count; i++) {
+                odev = minor_to_mdev(i);
+                if (!odev)
+                        continue;
+                if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
+                        continue;
+                if (!_drbd_may_sync_now(odev))
+                        rv |= (__drbd_set_state(_NS(odev, aftr_isp, 1), CS_HARD, NULL)
+                               != SS_NOTHING_TO_DO);
+        }
+
+        return rv;
+}
+
+/**
+ * _drbd_resume_next() - Resume resync on all devices that may resync now
+ * @mdev:       DRBD device.
+ *
+ * Called from process context only (admin command and worker).
+ */
+static int _drbd_resume_next(struct drbd_conf *mdev)
+{
+        struct drbd_conf *odev;
+        int i, rv = 0;
+
+        for (i = 0; i < minor_count; i++) {
+                odev = minor_to_mdev(i);
+                if (!odev)
+                        continue;
+                if (odev->state.conn == C_STANDALONE && odev->state.disk == D_DISKLESS)
+                        continue;
+                if (odev->state.aftr_isp) {
+                        if (_drbd_may_sync_now(odev))
+                                rv |= (__drbd_set_state(_NS(odev, aftr_isp, 0),
+                                                        CS_HARD, NULL)
+                                       != SS_NOTHING_TO_DO) ;
+                }
+        }
+        return rv;
+}
+
+void resume_next_sg(struct drbd_conf *mdev)
+{
+        write_lock_irq(&global_state_lock);
+        _drbd_resume_next(mdev);
+        write_unlock_irq(&global_state_lock);
+}
+
+void suspend_other_sg(struct drbd_conf *mdev)
+{
+        write_lock_irq(&global_state_lock);
+        _drbd_pause_after(mdev);
+        write_unlock_irq(&global_state_lock);
+}
+
+static int sync_after_error(struct drbd_conf *mdev, int o_minor)
+{
+        struct drbd_conf *odev;
+
+        if (o_minor == -1)
+                return NO_ERROR;
+        if (o_minor < -1 || minor_to_mdev(o_minor) == NULL)
+                return ERR_SYNC_AFTER;
+
+        /* check for loops */
+        odev = minor_to_mdev(o_minor);
+        while (1) {
+                if (odev == mdev)
+                        return ERR_SYNC_AFTER_CYCLE;
+
+                /* dependency chain ends here, no cycles. */
+                if (odev->sync_conf.after == -1)
+                        return NO_ERROR;
+
+                /* follow the dependency chain */
+                odev = minor_to_mdev(odev->sync_conf.after);
+        }
+}
+
+int drbd_alter_sa(struct drbd_conf *mdev, int na)
+{
+        int changes;
+        int retcode;
+
+        write_lock_irq(&global_state_lock);
+        retcode = sync_after_error(mdev, na);
+        if (retcode == NO_ERROR) {
+                mdev->sync_conf.after = na;
+                do {
+                        changes  = _drbd_pause_after(mdev);
+                        changes |= _drbd_resume_next(mdev);
+                } while (changes);
+        }
+        write_unlock_irq(&global_state_lock);
+        return retcode;
+}
+
+/**
+ * drbd_start_resync() - Start the resync process
+ * @mdev:       DRBD device.
+ * @side:       Either C_SYNC_SOURCE or C_SYNC_TARGET
+ *
+ * This function might bring you directly into one of the
+ * C_PAUSED_SYNC_* states.
+ */
+void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
+{
+        union drbd_state ns;
+        int r;
+
+        if (mdev->state.conn >= C_SYNC_SOURCE) {
+                dev_err(DEV, "Resync already running!\n");
+                return;
+        }
+
+        trace_drbd_resync(mdev, TRACE_LVL_SUMMARY, "Resync starting: side=%s\n",
+                          side == C_SYNC_TARGET ? "SyncTarget" : "SyncSource");
+
+        /* In case a previous resync run was aborted by an IO error/detach on the peer. */
+        drbd_rs_cancel_all(mdev);
+
+        if (side == C_SYNC_TARGET) {
+                /* Since application IO was locked out during C_WF_BITMAP_T and
+                   C_WF_SYNC_UUID we are still unmodified. Before going to C_SYNC_TARGET
+                   we check that we might make the data inconsistent. */
+                r = drbd_khelper(mdev, "before-resync-target");
+                r = (r >> 8) & 0xff;
+                if (r > 0) {
+                        dev_info(DEV, "before-resync-target handler returned %d, "
+                             "dropping connection.\n", r);
+                        drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
+                        return;
+                }
+        }
+
+        drbd_state_lock(mdev);
+
+        if (!get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                drbd_state_unlock(mdev);
+                return;
+        }
+
+        if (side == C_SYNC_TARGET) {
+                mdev->bm_resync_fo = 0;
+        } else /* side == C_SYNC_SOURCE */ {
+                u64 uuid;
+
+                get_random_bytes(&uuid, sizeof(u64));
+                drbd_uuid_set(mdev, UI_BITMAP, uuid);
+                drbd_send_sync_uuid(mdev, uuid);
+
+                D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
+        }
+
+        write_lock_irq(&global_state_lock);
+        ns = mdev->state;
+
+        ns.aftr_isp = !_drbd_may_sync_now(mdev);
+
+        ns.conn = side;
+
+        if (side == C_SYNC_TARGET)
+                ns.disk = D_INCONSISTENT;
+        else /* side == C_SYNC_SOURCE */
+                ns.pdsk = D_INCONSISTENT;
+
+        r = __drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
+        ns = mdev->state;
+
+        if (ns.conn < C_CONNECTED)
+                r = SS_UNKNOWN_ERROR;
+
+        if (r == SS_SUCCESS) {
+                mdev->rs_total     =
+                mdev->rs_mark_left = drbd_bm_total_weight(mdev);
+                mdev->rs_failed    = 0;
+                mdev->rs_paused    = 0;
+                mdev->rs_start     =
+                mdev->rs_mark_time = jiffies;
+                mdev->rs_same_csum = 0;
+                _drbd_pause_after(mdev);
+        }
+        write_unlock_irq(&global_state_lock);
+        drbd_state_unlock(mdev);
+        put_ldev(mdev);
+
+        if (r == SS_SUCCESS) {
+                dev_info(DEV, "Began resync as %s (will sync %lu KB [%lu bits set]).\n",
+                     drbd_conn_str(ns.conn),
+                     (unsigned long) mdev->rs_total << (BM_BLOCK_SHIFT-10),
+                     (unsigned long) mdev->rs_total);
+
+                if (mdev->rs_total == 0) {
+                        /* Peer still reachable? Beware of failing before-resync-target handlers! */
+                        request_ping(mdev);
+                        __set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(mdev->net_conf->ping_timeo*HZ/9); /* 9 instead 10 */
+                        drbd_resync_finished(mdev);
+                        return;
+                }
+
+                /* ns.conn may already be != mdev->state.conn,
+                 * we may have been paused in between, or become paused until
+                 * the timer triggers.
+                 * No matter, that is handled in resync_timer_fn() */
+                if (ns.conn == C_SYNC_TARGET)
+                        mod_timer(&mdev->resync_timer, jiffies);
+
+                drbd_md_sync(mdev);
+        }
+}
+
+int drbd_worker(struct drbd_thread *thi)
+{
+        struct drbd_conf *mdev = thi->mdev;
+        struct drbd_work *w = NULL;
+        LIST_HEAD(work_list);
+        int intr = 0, i;
+
+        sprintf(current->comm, "drbd%d_worker", mdev_to_minor(mdev));
+
+        while (get_t_state(thi) == Running) {
+                drbd_thread_current_set_cpu(mdev);
+
+                if (down_trylock(&mdev->data.work.s)) {
+                        mutex_lock(&mdev->data.mutex);
+                        if (mdev->data.socket && !mdev->net_conf->no_cork)
+                                drbd_tcp_uncork(mdev->data.socket);
+                        mutex_unlock(&mdev->data.mutex);
+
+                        intr = down_interruptible(&mdev->data.work.s);
+
+                        mutex_lock(&mdev->data.mutex);
+                        if (mdev->data.socket  && !mdev->net_conf->no_cork)
+                                drbd_tcp_cork(mdev->data.socket);
+                        mutex_unlock(&mdev->data.mutex);
+                }
+
+                if (intr) {
+                        D_ASSERT(intr == -EINTR);
+                        flush_signals(current);
+                        ERR_IF (get_t_state(thi) == Running)
+                                continue;
+                        break;
+                }
+
+                if (get_t_state(thi) != Running)
+                        break;
+                /* With this break, we have done a down() but not consumed
+                   the entry from the list. The cleanup code takes care of
+                   this...   */
+
+                w = NULL;
+                spin_lock_irq(&mdev->data.work.q_lock);
+                ERR_IF(list_empty(&mdev->data.work.q)) {
+                        /* something terribly wrong in our logic.
+                         * we were able to down() the semaphore,
+                         * but the list is empty... doh.
+                         *
+                         * what is the best thing to do now?
+                         * try again from scratch, restarting the receiver,
+                         * asender, whatnot? could break even more ugly,
+                         * e.g. when we are primary, but no good local data.
+                         *
+                         * I'll try to get away just starting over this loop.
+                         */
+                        spin_unlock_irq(&mdev->data.work.q_lock);
+                        continue;
+                }
+                w = list_entry(mdev->data.work.q.next, struct drbd_work, list);
+                list_del_init(&w->list);
+                spin_unlock_irq(&mdev->data.work.q_lock);
+
+                if (!w->cb(mdev, w, mdev->state.conn < C_CONNECTED)) {
+                        /* dev_warn(DEV, "worker: a callback failed! \n"); */
+                        if (mdev->state.conn >= C_CONNECTED)
+                                drbd_force_state(mdev,
+                                                NS(conn, C_NETWORK_FAILURE));
+                }
+        }
+        D_ASSERT(test_bit(DEVICE_DYING, &mdev->flags));
+        D_ASSERT(test_bit(CONFIG_PENDING, &mdev->flags));
+
+        spin_lock_irq(&mdev->data.work.q_lock);
+        i = 0;
+        while (!list_empty(&mdev->data.work.q)) {
+                list_splice_init(&mdev->data.work.q, &work_list);
+                spin_unlock_irq(&mdev->data.work.q_lock);
+
+                while (!list_empty(&work_list)) {
+                        w = list_entry(work_list.next, struct drbd_work, list);
+                        list_del_init(&w->list);
+                        w->cb(mdev, w, 1);
+                        i++; /* dead debugging code */
+                }
+
+                spin_lock_irq(&mdev->data.work.q_lock);
+        }
+        sema_init(&mdev->data.work.s, 0);
+        /* DANGEROUS race: if someone did queue his work within the spinlock,
+         * but up() ed outside the spinlock, we could get an up() on the
+         * semaphore without corresponding list entry.
+         * So don't do that.
+         */
+        spin_unlock_irq(&mdev->data.work.q_lock);
+
+        D_ASSERT(mdev->state.disk == D_DISKLESS && mdev->state.conn == C_STANDALONE);
+        /* _drbd_set_state only uses stop_nowait.
+         * wait here for the Exiting receiver. */
+        drbd_thread_stop(&mdev->receiver);
+        drbd_mdev_cleanup(mdev);
+
+        dev_info(DEV, "worker terminated\n");
+
+        clear_bit(DEVICE_DYING, &mdev->flags);
+        clear_bit(CONFIG_PENDING, &mdev->flags);
+        wake_up(&mdev->state_wait);
+
+        return 0;
+}
diff --git a/drivers/block/drbd/drbd_wrappers.h b/drivers/block/drbd/drbd_wrappers.h
new file mode 100644
index 000000000000..f93fa111ce50
--- /dev/null
+++ b/drivers/block/drbd/drbd_wrappers.h
@@ -0,0 +1,91 @@
+#ifndef _DRBD_WRAPPERS_H
+#define _DRBD_WRAPPERS_H
+
+#include <linux/ctype.h>
+#include <linux/mm.h>
+
+/* see get_sb_bdev and bd_claim */
+extern char *drbd_sec_holder;
+
+/* sets the number of 512 byte sectors of our virtual device */
+static inline void drbd_set_my_capacity(struct drbd_conf *mdev,
+                                        sector_t size)
+{
+        /* set_capacity(mdev->this_bdev->bd_disk, size); */
+        set_capacity(mdev->vdisk, size);
+        mdev->this_bdev->bd_inode->i_size = (loff_t)size << 9;
+}
+
+#define drbd_bio_uptodate(bio) bio_flagged(bio, BIO_UPTODATE)
+
+static inline int drbd_bio_has_active_page(struct bio *bio)
+{
+        struct bio_vec *bvec;
+        int i;
+
+        __bio_for_each_segment(bvec, bio, i, 0) {
+                if (page_count(bvec->bv_page) > 1)
+                        return 1;
+        }
+
+        return 0;
+}
+
+/* bi_end_io handlers */
+extern void drbd_md_io_complete(struct bio *bio, int error);
+extern void drbd_endio_read_sec(struct bio *bio, int error);
+extern void drbd_endio_write_sec(struct bio *bio, int error);
+extern void drbd_endio_pri(struct bio *bio, int error);
+
+/*
+ * used to submit our private bio
+ */
+static inline void drbd_generic_make_request(struct drbd_conf *mdev,
+                                             int fault_type, struct bio *bio)
+{
+        __release(local);
+        if (!bio->bi_bdev) {
+                printk(KERN_ERR "drbd%d: drbd_generic_make_request: "
+                                "bio->bi_bdev == NULL\n",
+                       mdev_to_minor(mdev));
+                dump_stack();
+                bio_endio(bio, -ENODEV);
+                return;
+        }
+
+        if (FAULT_ACTIVE(mdev, fault_type))
+                bio_endio(bio, -EIO);
+        else
+                generic_make_request(bio);
+}
+
+static inline void drbd_plug_device(struct drbd_conf *mdev)
+{
+        struct request_queue *q;
+        q = bdev_get_queue(mdev->this_bdev);
+
+        spin_lock_irq(q->queue_lock);
+
+/* XXX the check on !blk_queue_plugged is redundant,
+ * implicitly checked in blk_plug_device */
+
+        if (!blk_queue_plugged(q)) {
+                blk_plug_device(q);
+                del_timer(&q->unplug_timer);
+                /* unplugging should not happen automatically... */
+        }
+        spin_unlock_irq(q->queue_lock);
+}
+
+static inline int drbd_crypto_is_hash(struct crypto_tfm *tfm)
+{
+        return (crypto_tfm_alg_type(tfm) & CRYPTO_ALG_TYPE_HASH_MASK)
+                == CRYPTO_ALG_TYPE_HASH;
+}
+
+#ifndef __CHECKER__
+# undef __cond_lock
+# define __cond_lock(x,c) (c)
+#endif
+
+#endif